Assembled cartilage repair graft

ABSTRACT

Bifunctional and assembled implants are provided for osteochondral implantation.

RELATED APPLICATIONS

This application claims priority to, and is a continuation of, U.S.patent application Ser. No. 12/140,210, having a filing date of Jun. 16,2008, now abandoned, which is incorporated herein by reference, andwhich also claims priority to PCT Patent Application No.PCT/US2009/047327, having a filing date of Jun. 15, 2009, all of whichare incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

Focal articular cartilage defects of the knee are not uncommonconsequences of injuries from sports, work or activities of dailyliving. Arthroscopic studies have estimated the occurrence of near fullthickness lesions, full thickness lesions or full thickness with boneyinvolvement lesions greater than 1 cm² to be in the range of 6% of allsurgical procedures in the knee. These types of articular cartilagedefects may cause pain, swelling and/or knee locking and thus diminishthe individual's overall quality of life. The size (area dimensions),depth (partial cartilage tissue to boney involvement), containment,co-morbidities (e.g., ACL tear, meniscal tear, and malalignment) andregion of a defect will influence the procedure used by surgeons.Currently, for focal defects smaller than (<) 2.5 cm², the subject andsurgeon have few options: debridement (chondroplasty), marrowstimulation (micro-fracture, abrasionoplasty, or subchondral drilling),or autograft osteochondral plugs (OATS, COR, mosaicoplasty). For defectsgreater than (>) 2.5 cm², the options are allograft osteochondral plugsor autologous cultured chondrocytes (e.g. Carticel® in the UnitedStates). While these procedures show significant rates of clinicalsuccess in the short and medium term, they each have limitations rangingfrom the quality of the cartilage repair to the cost and complexity ofsurgical procedures. Additionally, some of the procedures themselvescreate defects (i.e. OATS) either as a direct result of the primaryprocedure or through second site morbidity caused by the recovery of thepatient's own tissue.

The surfaces of joints that face the joint cavity are covered with amechanically robust connective tissue layer called chondral surface orcartilage layer. Underneath the cartilage layer is a cancellous bonetermed subchondral bone. The chondral surface or cartilage layer is theprimary functional surface of joints such as the knee, elbow, orshoulder. The cartilage cushions shock, carries the compressive loadsplaced on the joint, and allows for smooth and controlled movementbetween the bones in the joint. The subchondral bone supports thecartilage layer by providing blood flow, nutrients and structuralintegrity.

BRIEF SUMMARY OF THE INVENTION

The present invention provides assembled implants and articularcartilage repair implants particularly useful in the field of orthopedicor sports medicine surgery, and generally useful for the repair,replacement and regrowth of articulating cartilage surfaces.

In one aspect of the present invention, a bifunctional bioabsorbableassembled implant adapted for implantation at a site of a bone cartilagejunction is provided. The bifunctional implant has the ability topromote growth of at least two different tissue types, such as cartilageand bone, at adjacent areas of a single implant site. The bifunctionalimplant preferably has an osteoconductive portion adapted to fill adefect in a subchondral bone layer, and a chondroinductive portionadapted to fill a corresponding cartilage layer. The osteoconductiveportion and the chondroinductive portion are derived from the same ordifferent source materials and preferably are assembled in a stackedrelationship.

A bifunctional implant is particularly beneficial in the treatment ofosteochondral defects in an articulating cartilage joint surface. Anosteoconductive portion of the implant provides proper physicalproperties for implantation and anchoring of the implant while promotingthe ingrowth and healing of the underlying subchondral bone tissue. Anosteoconductive portion further provides the proper biomechanicalproperties to support and maintain the implant during remodeling,including sufficient porosity (or permeability), strength and stiffnessapproximating those of native subchondral bone. A chondroinductiveportion provides the proper physical properties to support anatomicalloads and maintain integrity of the joint while promoting the ingrowthand healing of native cartilaginous tissue. A chondroinductive portionfurther provides the proper biomechanical properties to support andmaintain the implant during remodeling, including sufficient porosity(or permeability), strength and stiffness approximating those of nativecartilaginous tissue.

In another aspect an assembled cartilage repair implant, suitable forimplant at an osteochondral site in a human patient, and assembled via ahydration controlled interference fit is provided, including at leastone osteoconductive cancellous bone portion, and at least onechondroinductive demineralized cortical bone portion. The cancellousbone portion and the cortical bone portion are preferably assembled in astacked relationship.

In another aspect an assembled biological implant shaped and sized forimplantation into a bone cartilage junction is provided, having a firstregion of osteoconductive cancellous bone material and a second regionof chondroinductive cortical bone material, wherein the first and secondregions are joined by a hydration controlled shrink fit. In someembodiments, the first region is a lower region or base, and the secondregion is an upper region or cap.

In another aspect of the present invention an implant adapted forimplantation at an articulating cartilage site is provided, having aperforated membrane of demineralized cortical bone. The membrane definesa plane by the membrane's length and width (its longer dimensions). Themembrane includes natural Haversian canals oriented in the plane of themembrane. Natural Haversian canals oriented generally parallel to or atan oblique angle to the plane of the membrane may advantageously providetransport, signaling, and growth pathways between or in addition to anyadded perforation, canals or other features to support ingrowth,chondroinduction and chondroconduction.

In another embodiment, the membrane is recovered from a long bone in aradial section wherein the Haversian canals are oriented transverse tothe thickness of the membrane, running along either the length or widthof the membrane, or both. In this alternative embodiment, holes aredrilled or otherwise formed across the thickness of the membrane afterdemineralization to provide a chondroinductive membrane.

In another aspect of the present invention, a method of using anassembled cartilage repair implant is provided, including filling anosteochondral defect having a subchondral bone layer and a cartilaginouslayer with an assembled implant adapted for implantation at a bonecartilage junction. The assembled implant includes at least oneosteoconductive or synthetic portion, preferably of cancellous bone, andat least one chondroinductive portion, preferably of demineralizedcortical bone, such that the subchondral bone layer of the defect isfilled with the osteoconductive (or synthetic) portion, and thecartilaginous layer of the defect is filled with the chondroinductivedemineralized cortical bone portion.

In another aspect a method is provided for the treatment ofcartilaginous tissue in a mammal, including filling a defect site withan assembled bifunctional biological implant adapted for implantation ata bone cartilage junction, such that a first region of the defect siteis filled by osteoconductive cancellous bone material and a secondregion of the defect site is filled by chondroinductive cortical bonematerial. In some embodiments, the first region is a lower region orbase, and the second region is an upper region or cap.

In another aspect a method of making a bifunctional bioabsorbableassembled implant adapted for implantation at the site of a bonecartilage junction is provided, including the steps of providing anosteoconductive portion adapted to fill a defect in a subchondral bonelayer, and assembling the osteoconductive portion with achondroinductive portion adapted to fill a cartilage layer, wherein theosteoconductive portion and the chondroinductive portion are assembledvia a hydration controlled interference fit.

In another aspect a method is provided for making an assembledbiological implant shaped and sized for implantation into a bonecartilage junction, including the steps of providing a first region ofcortical bone material in a dehydrated state, and assembling thecortical bone material with a second region of cancellous bone material,wherein the dehydrated cortical bone material is rehydrated afterassembly.

In another aspect, a method of making an assembled bifunctional implantis provided, including the steps of: providing a portion of mineralizedcortical bone in a hydrated state; machining the portion of mineralizedcortical bone to produce a hydrated machined mineralized cortical boneportion; demineralizing the hydrated machined mineralized cortical boneportion to produce a hydrated machined demineralized cortical boneportion; dehydrating the hydrated machined demineralized cortical boneportion, to produce a dehydrated machined demineralized cortical boneportion; providing a portion of mineralized cancellous bone, which isdehydrated, partially hydrated or hydrated; assembling the dehydratedmachined demineralized cortical bone portion and the mineralizedcancellous bone portion, and rehydrating at least one of the boneportions assembled together, to produce a hydration controlledinterference fit in the assembly. In some embodiments, at least onegeometric feature of the assembly or of one of the assembled boneportions is machined to a predetermined dimension. Optionally, thehydrated machined mineralized cancellous bone portion may also bedemineralized.

The present implants have been shown to produce a particularly preferredembodiment with a combination of assembled elements including asubstantially cylindrical chondroinductive portion, having at least onesubstantially flat, smooth or rounded end surface, assembled from twopieces of chondroinductive demineralized cortical bone, alternativelyassembled from three or four pieces of chondroinductive demineralizedcortical bone. The pieces of demineralized cortical bone are preferablysubstantially similar, mirrored, or radially symmetric with respect toeach other. Alternatively, a single piece of substantially cylindricalchondroinductive demineralized cortical bone, preferably having at leastone substantially flat, smooth or rounded end surface, may be usedeffectively, especially when producing smaller size implants, whereinthe chondroinductive demineralized cortical bone piece is preferablyradially symmetric or symmetric about a plane passing through its centeraxis, or both.

The chondroinductive portion(s) of this particularly preferredembodiment are assembled together, or held in place in the case of asingle piece of chondroinductive demineralized cortical bone, by ahydration controlled interference fit which is also a shrink fit and anegatively tapered shaft and bore fit, with a substantially cylindricalosteoconductive portion of mineralized cancellous bone, the cancellousportion preferably having at least one substantially flat, smooth orrounded end surface. In this embodiment, the osteoconductive piece ofmineralized cancellous bone completely surrounds a part of thechondroinductive portion to capture and secure it in place.

The outer substantially cylindrical profile of the implant, formed bythe union of a substantially cylindrical chondroinductive portion,preferably having at least one substantially flat, smooth or rounded endsurface, assembled from two pieces of chondroinductive demineralizedcortical bone together with a substantially cylindrical osteoconductivepiece of mineralized cancellous bone, preferably having at least onesubstantially flat, smooth or rounded end surface, provides an implantadapted for insertion with widely used arthroscopic surgical technique,instrumentation and fixation.

A further advantage of this embodiment, especially when an assembledchondroinductive portion is used, is that the negatively tapered shaftand bore fit provides solid and secure assembly wherein the at least twopieces of chondroinductive demineralized cortical bone are in directcontact with each other and are completely or partially surrounded overat least a part of their surface at the hydration controlledinterference fit interface by a piece of osteoconductive cancellousbone.

An advantage of the assembly methods, and especially of the hydrationcontrolled interference fit or hydration controlled shrink fit, is thatthe assembled implants are suitable for implantation at an osteochondralsite in a human or other mammal without additional internal fasteners orconnective elements such as press fit pins, bone pins, sutures, oradhesives. In addition to requiring excess material and additionalprocessing steps, these other fasteners or connective elements add extracost and complications to the design, manufacture and use of theimplants. A preferred embodiment of the present invention provides anassembly that does not comprise separate fasteners or adhesive forholding together the implant.

Alternatively, certain embodiments of the present implants provide anassembly including additional internal fasteners or connective elementssuch as press fit pins, bone pins, sutures, or adhesives. Theseadditional external fasteners may be employed either in conjunction withor in place of a hydration controlled interference fit to provideadditional strength or reinforcement, or to provide additional elementssuch as growth factors, cells or specific scaffold materials to promotehealing, chondroinduction, osteoinduction or osteoconduction.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIGS. 1A-1D show perspective views of each of four different steps inthe process of making one embodiment of the present implants.

FIG. 2 shows a perspective cross sectional view of an implant implantedat an osteochondral surgical site by the present methods.

FIGS. 3A-3D show a series of cross sectional views of a negativelytapered hydration controlled interference fit assembled implant,including (A) a chondroinductive portion and an osteoconductive portion;(B) a dehydrated chondroinductive portion in position for assembly justabove an osteoconductive portion; (C) an assembly of a dehydratedchondroinductive portion mated with an osteoconductive portion; and (D)a fully hydrated interference fit between a hydrated chondroinductiveportion and a hydrated osteoconductive portion.

FIGS. 4A-4D show a series of cross sectional views of a positivelytapered hydration controlled interference fit assembled implant,including (A) a chondroinductive portion and an osteoconductive portion;(B) a dehydrated chondroinductive portion in position for assembly justabove an osteoconductive portion; (C) an assembly of a dehydratedchondroinductive portion mated with an osteoconductive portion; and (D)a fully hydrated interference fit between a hydrated chondroinductiveportion and a hydrated osteoconductive portion.

FIGS. 5A-5D show a series of cross sectional views of a non taperedhydration controlled interference fit assembled implant, including (A) achondroinductive portion and an osteoconductive portion; (B) adehydrated chondroinductive portion in position for assembly just abovean osteoconductive portion; (C) an assembly of a dehydratedchondroinductive portion mated with an osteoconductive portion; and (D)a fully hydrated interference fit between a hydrated chondroinductiveportion and a hydrated osteoconductive portion.

FIGS. 6A-6D show a series of cross sectional views of a non taperedundercut step or counter bore hydration controlled interference fitassembled implant, including (A) a chondroinductive portion and anosteoconductive portion; (B) a dehydrated chondroinductive portion inposition for assembly just above an osteoconductive portion; (C) anassembly of a dehydrated chondroinductive portion mated with anosteoconductive portion; and (D) a fully hydrated interference fitbetween a hydrated chondroinductive portion and a hydratedosteoconductive portion.

FIGS. 7A-7D show a series of cross sectional views of a negativelytapered hydration controlled interference fit assembled implant,including (A) a chondroinductive portion and an osteoconductive portion;(B) a dehydrated chondroinductive portion in position for assembly justabove an osteoconductive portion; (C) an assembly of a dehydratedchondroinductive portion mated with an osteoconductive portion; and (D)a fully hydrated interference fit between a hydrated chondroinductiveportion and a hydrated osteoconductive portion.

FIGS. 8A-8D show top, perspective, section and side views, respectively,of an assembled implant wherein the chondroinductive cap is smaller thanthe osteoconductive base.

FIGS. 9A-9D show top, perspective, section and side views, respectively,of an assembled implant wherein the chondroinductive cap is larger thanthe osteoconductive base.

FIGS. 10A-10D show top, perspective, section and side views,respectively, of an assembled implant wherein the chondroinductive capis substantially or about the same size as the osteoconductive base.

FIG. 11A shows a perspective view of a chondroinductive washer portion.

FIGS. 11B-11F show a series of cross sectional views of negativelytapered, non-tapered, positively tapered, threaded and expandingembodiments, respectively, of a hydration controlled interference fitassembled implant, each including a chondroinductive portion assembledwith or just above an osteoconductive portion.

FIG. 12A shows a perspective view of a unitary anchored cap implant,including a chondroinductive portion and an osteoconductive portion.

FIGS. 12B-12F show a series of cross sectional views of negativelytapered, non-tapered, positively tapered, threaded and expandingembodiments, respectively, of a unitary anchored cap implant, eachincluding a chondroinductive portion formed together with or just abovean osteoconductive portion.

FIGS. 13A-13C show a series of views of relaxed, bent and implantedstates, respectively, of a unitary undercut chondroinductive washerimplant, each including a chondroinductive portion with an undercut edgeand an optional graft manipulation or fixation hole.

FIGS. 14A-14D show top, perspective, section and side views,respectively, of a chondroinductive membrane implant with pre-machinedfixation holes.

FIGS. 15A-15C show a series of cross sectional views of an osteochondralsurgical site for a primary plug procedure (A) in the disease state, (B)after creation of the primary surgical defect or core, and (C) followingrepair with an implant, respectively, wherein one or more implants areimplanted by the present methods. FIG. 15D shows a top or plan view ofan overlapping multiple implant configuration (“snowman” configuration).

FIGS. 16A-16E show a series of cross sectional views of an osteochondralsurgical site for a secondary or backfill plug procedure in the diseasestate, after creation of the primary surgical defect or core, aftercreation of the secondary plug core, following repair of the primarydefect with the secondary core, and following repair of the secondary orbackfill defect with an implant, respectively, wherein one or moreimplants are implanted by the present methods.

FIGS. 17A-17C show a series of orthogonal views of the shaft of a longbone, wherein the cortical bone source material is recovered,advantageously producing an implant having naturally occurring internalcanals. FIG. 17D shows an exploded perspective view of a hemicylindrical cortical bone portion blank cut from a section of the shaftof a long bone.

FIGS. 18A and 18B show a series of views of the condyle of a long bone,wherein the cancellous bone source material is recovered, advantageouslyproducing an implant having optimal density and quality of cancellousbone for the formation of an osteoconductive base.

FIG. 19 shows a perspective cross sectional view of an implant implantedat an osteochondral surgical site by the present methods.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides bifunctional implants useful in thereplacement and repair of damaged cartilaginous or articular cartilagetissue. The invention also provides assembled implants comprising achondroinductive portion and an osteoconductive portion assembled toform a bifunctional implant. The invention further provides assembledimplants having a top portion or cap of chondroinductive demineralizedcortical bone assembled in a hydration controlled interference fit witha bottom portion or base of osteoconductive mineralized cancellous boneto form a bifunctional implant matched to the anatomy of anosteoarticular surgical site and suited to the arthroscopic repair ofosteoarticular defects.

The present disclosure describes bifunctional implants suitable for nonload bearing and lower wear application such as the backfill ofautograft core harvest sites where the autograft tissue is used as theimplant plug in the primary damage repair site (e.g. OATS procedure).The present disclosure further describes bifunctional implants suitablefor load bearing and high wear applications such as direct implantationin the primary surgically created defect replacing a section of diseasedcartilaginous or osteochondral tissue.

As one of the preferred embodiments, a cylindrical bifunctionalbiological assembled implant is provided which is adapted forimplantation at the site of a bone cartilage junction, with anosteoconductive mineralized cancellous allograft bone portion adapted tofill a defect in a subchondral bone layer assembled in a stackedrelationship with a chondroinductive demineralized cortical allograftbone portion adapted to fill a corresponding cartilage layer.Cylindrical implants are preferred for their ease of use andcompatibility with known surgical methods and instruments.

Current instrument sets utilize hollow cylindrical coring bits, drillsor punches to make circular or cylindrical cuts and defects at theosteochondral site. These cylindrical instruments produce generallycylindrical autograft plugs and generally cylindrical osteochondraldefects or surgically created defects. Instrumentation designed forrecovery, transport, handling and implantation of osteochondral implantsalso makes use of hollow cylindrical geometry to manage these implants,cores, or transplants. Therefore, the manufacture of cylindricalimplants is highly preferred not only for its rotational symmetry, easeof manufacture and absence of stress concentrations, but also for itsease of implantation and compatibility with currently availableinstrumentation sets.

Although cylindrical implant configurations are used extensively toexemplify embodiments of the present implants throughout thespecification and figures, it is contemplated that the implants andmethods of the present invention are operable with other implantconfigurations, including polygonal, square, rectangular, triangular,substantially cylindrical, substantially square, substantiallytriangular, substantially rectangular, rectilinear, curvilinear,arcuate, non-arcuate, and irregular implant body shapes.

In some embodiments, the present implants provide a concave, convex,irregular or complexly curved upper surface, adapted to approximate thesurface geometry of an articulating cartilage site, advantageouslyreducing peak forces on the implant during rehabilitation and remodelingfollowing surgery. In other embodiments the implants advantageouslyprovide concave, convex, arcuate, non-arcuate, planar, non-planar orirregular surfaces at the interface between two portions or between twopieces in the assembly or at the external interface between the implantand the surgical site. These shapes are advantageously employed toenhance placement, orientation or fixation of the implant or betweenelements of the assembly.

The chondroinductive portion is preferably sized to substantiallyapproximate the depth of the cartilage layer at a site of implantation.The osteoconductive portion is preferably sized to at least about 1.5times the depth of the chondroinductive portion, to allow a solidfixation at the surgical site and to prevent dislodgement of the implantfollowing surgery.

The osteoconductive portions and chondroinductive portions each define acharacteristic depth and a characteristic width or characteristicdiameter. In one embodiment, the characteristic depth of theosteoconductive portion is substantially equivalent to or greater thanthe characteristic depth of the chondroinductive portion. In anotherembodiment, the characteristic depth of the osteoconductive portion isat least about one and one half times greater than the characteristicdepth of the chondroinductive portion, and the characteristic width ofthe osteoconductive portion is greater than the characteristic width ofthe chondroinductive portion. Various other ratios of width and depthare contemplated, as well as alternative configurations including morethan two portions.

An interference fit exists when two or more parts are assembled togetherwith interference in the mating dimension or dimensions, such that twoor more parts attempt to occupy the same space. The stress created asone or more of the parts attempts to occupy the same space with theother results in forces which generally act to hold the assemblytogether. Interference fits are generally accomplished either by forcingor pressing the interfering parts together in a press fit, or bycreating a condition, typically by heating and cooling and/or by addingor removing moisture, where the parts are without interference duringthe assembly process and then shrink or swell to a create aninterference fit. Shrinkage and swelling of a chondroinductive portionmay be a variable phenomenon across a given geometry, sometimesresulting in warping or deformation of a dehydrated part. Uponrehydration, however, most materials will return substantially to theiroriginal shape. An interference fit, press fit or shrink fit may includea straight or tapered shaft and bore fit.

The pieces assembled together may include an osteoconductive portion anda chondroinductive demineralized cortical bone portion having a seriesof canals. The canals may be manufactured or naturally occurring in thebone material, and may be oriented in a direction communicating betweenthe osteoconductive portion and at least one surface of thechondroinductive demineralized cortical bone portion. The canals arepreferably oriented in alignment with or substantially parallel to amajor axis of the interference fit, press fit, or shrink fit. Forexample, the canals may be oriented such that they travel in a directionalong the axis of the cylinder or bore in a bore and cylinderinterference fit. In a preferred embodiment, naturally occurringHaversian canals of the cortical bone material are in substantialalignment with a major body axis of the implant, and/or in communicationwith one or more end surfaces of the implant. Alternatively, the canals,or a majority or substantial percentage of the canals, may be orientedat an angle to or perpendicular to a major axis of the interference fit,press fit, or shrink fit.

The implants of the present invention may have a graft manipulationhole, which is advantageous for aiding graft placement and may alsoserve as an additional conduit or channel allowing access of blood andother fluids from the surgical implantation site into the implantinterior (in addition to any natural or artificial canals present in theimplant). Such holes are preferably in the base portion of an assembledimplant or in the central or edge areas of a membrane implant. When theimplant is a membrane type implant, the hole is preferably pre-machined,formed or punched and may be used for fixation of the implant. Theimplant may have one or more of these fixation holes, depending onconfiguration. Fixation devices for use in these holes may be, but arenot limited to, suture, pins, staples, and bone pins When the implant isan assembled implant having a cap and a base portion, if the basematerial is porous, such as cancellous bone material, the hole isoptional and may be replaced by a flat bottom in the base portion,providing additional strength and structural integrity.

The Figures, and the discussion thereof, provided in this disclosurerelate to various embodiments of the present technology. It should beunderstood that the Figures are illustrative in nature, and thatmodifications can be made thereto without departing from the scope ofthe present invention.

FIGS. 1A-1D show perspective views of each of four different steps inthe process of making one embodiment of the present implants.

FIG. 1A shows a perspective view of one fully hydrated piece 100 of aportion suitable for assembly in an implant having a cylindrical profile101, flat top portion 102, a flat mating surface 103, a negativelytapered shaft 104, and a flat bottom surface 105. Features 101 to 105are shown in the fully hydrated or as machined state in FIG. 1A. Thepiece 100 may be assembled with another piece of the same or ofdifferent design to form a chondroinductive portion, and is preferablymachined from cortical bone, then demineralized.

FIG. 1B shows a perspective view of one dehydrated piece 110 of aportion suitable for assembly in an implant having a shrunken but stillsubstantially cylindrical profile 111, a shrunken but stillsubstantially flat top portion 112, a shrunken and withdrawn flat matingsurface 113, a shrunken negatively tapered shaft 114, and a shrunken butstill substantially flat bottom surface 115. Features 111 to 115 areshown in the dehydrated or shrunken state in FIG. 1B. The piece 110 maybe assembled with another piece of the same or of different design toform a chondroinductive portion, and is preferably machined fromcortical bone, then demineralized.

FIG. 1C shows a perspective view of an exploded or in process view of a3 piece assembly 120. Pieces 121 and 122 are dehydrated pieces,preferably chondroinductive and preferably of demineralized corticalbone, aligned in position for assembly with a third piece 123. Piece 123is a base portion, preferably osteoconductive and preferably ofmineralized cancellous bone, aligned in position for assembly withpieces 121 and 122. Piece 123 has a bore 124 which is of substantiallyequivalent diameter or slightly larger than shaft 125 formed by the twopieces 121 and 122 in their dehydrated state. A gap 126 is visiblebetween the mating faces of dehydrated piece 121 and dehydrated piece122.

FIG. 1D shows a perspective view of a fully hydrated complete assemblyof a bifunctional implant 130. Pieces 131 and 132 are assembled to forma top or cap portion with base portion 133. The mating features (notshown) are preferably a negatively tapered shaft and bore, hydrationcontrolled shrink fit. The implant has a characteristic width ordiameter 134 and a characteristic depth, thickness or height 135. Themating faces of each of piece 131 and 132, respectively, meet to form asubstantially flat interface 136 between the two pieces 131 and 132which together make up the cap portion 137.

FIG. 2 shows a perspective cross sectional view of a cylindricalcartilage repair implant 201 implanted at an osteochondral surgical site200 by the present methods. A surgically created defect 202 passesthrough a cartilage layer 203, through a narrow cortical bone shelllayer 204 a and into a subchondral bone layer 204 of the patient. Achondroinductive demineralized cortical bone cap portion 205 fills thetop region of the surgical defect 202 within the cartilage layer 203. Anosteoconductive cancellous bone base portion 206 fills the bottom regionof the surgical defect 202 within the subchondral bone layer 204. Capportion 205 is assembled from two pieces 205 a and 205 b, which meet atseam 206, visible along the top of implant 201 and through the crosssection. A negatively tapered shaft and bore interference fit holdspieces 205 a and 205 b together with base 206. Natural Haversian canals208 are substantially in alignment with the major axis of implant 201and in communication between base portion 206 and top surface 209 of capportion 205 as well as with the subchondral bone layer 204 of thepatient.

FIGS. 3A-3D show a series of cross sectional views of a negativelytapered hydration controlled interference fit assembled implant. Thecross sectional views of FIGS. 3A-3D preferably represent cross sectionsof a cylindrical implant; but may alternatively represent extruded ormirrored sections producing rectilinear, slotted, triangular, square orpolygonal implants; or projected, swept or variable sections producingimplants of irregular or varying cross section.

FIG. 3A shows side by side cross sectional views of two implantembodiments, one with assembled cap pieces 301 and 302 mating with baseportion 303 to form a three piece assembly 300, and the other with amono cap portion 311 mating with base portion 313 to form a two pieceassembly 310. Bore 304 and bore 314 are adapted to mate with shaft 305and shaft 315, respectively. An optional hole 306 is provided as anadvantageous graft manipulation hole and as an additional conduit orchannel allowing access of blood and other fluids from the surgicalimplantation site into the implant interior. When the base material isporous, such as cancellous bone material, the optional hole 306 may bereplaced by a flat bottom 316 in the base portion 313, providingadditional strength and structural integrity.

FIG. 3B shows side by side cross sectional views of two implantembodiments 320 and 330, with dehydrated chondroinductive portions 321and 331 in position for assembly just above osteoconductive portions 322and 332, respectively. Dehydrated chondroinductive portions 321 and 331exhibit reduced diameter dimensions including shaft dimensions 323 and333, respectively, which are smaller than or substantially equal to boredimensions 324 and 334, respectively. For clarity and ease ofunderstanding, other shrinkage and warping effects such as the drawingin, curling, warping or curving of shafts 325 and 335, respectively, arenot shown.

FIG. 3C shows side by side cross sectional views of two implantembodiments 340 and 350, with an assembly of dehydrated chondroinductivecap portions 341 and 351 mated with osteoconductive base portions 342and 352, respectively. Dehydrated assembly clearance gaps 343 and 353,respectively, are visible around the shaft and bore fits of the twoimplant embodiments. Optional bottom clearance gaps 344 and 354,respectively, are visible in the assemblies, advantageously providingadditional clearance to allow for manufacturing and assembly tolerancesand providing a further interior path for infiltration, flow andtransport of blood and fluids within the implant. Optionally, bottomclearance gaps 344 and 354 may be eliminated or made to an interferencefit condition to maximize structural integrity and surface to surfacecontact within the graft interior.

FIG. 3D shows side by side cross sectional views of two implantembodiments 360 and 370, with fully hydrated interference fits 363 and373, between hydrated chondroinductive portions 361 and 371 andosteoconductive portions 362 and 372, respectively.

FIGS. 4A-4D show a series of cross sectional views of a positivelytapered hydration controlled interference fit assembled implant. Thecross sectional views of FIGS. 4A-4D preferably represent cross sectionsof a cylindrical implant; but may alternatively represent extruded ormirrored sections producing rectilinear, slotted, triangular, square orpolygonal implants; or projected, swept or variable sections producingimplants of irregular or varying cross section.

FIG. 4A shows side by side cross sectional views of two implantembodiments, one with assembled cap pieces 401 and 402 mating with baseportion 403 to form a three piece assembly 400, and the other with amono cap portion 411 mating with base portion 413 to form a two pieceassembly 410. Bore 404 and bore 414 are adapted to mate with shaft 405and shaft 415, respectively. An optional hole 406 is provided as anadvantageous graft manipulation hole and as an additional conduit orchannel allowing access of blood and other fluids from the surgicalimplantation site into the implant interior. When the base material isporous, such as cancellous bone material, the optional hole 406 may bereplaced by a flat bottom 416 in the base portion 413, providingadditional strength and structural integrity.

FIG. 4B shows side by side cross sectional views of two implantembodiments 420 and 430, with dehydrated chondroinductive portions 421and 431 in position for assembly just above osteoconductive portions 422and 432, respectively. Dehydrated chondroinductive portions 421 and 431exhibit reduced diameter dimensions including shaft dimensions 423 and433, respectively, which are smaller than or substantially equal to boredimensions 424 and 434, respectively. For clarity and ease ofunderstanding, other shrinkage and warping effects such as the drawingin, curling, warping or curving of shafts 425 and 435, respectively, arenot shown.

FIG. 4C shows side by side cross sectional views of two implantembodiments 440 and 450, with an assembly of dehydrated chondroinductivecap portions 441 and 451 mated with osteoconductive base portions 442and 452, respectively. Dehydrated assembly clearance gaps 443 and 453,respectively, are visible around the shaft and bore fits of the twoimplant embodiments. Optional bottom clearance gaps 444 and 454,respectively, are visible in the assemblies, advantageously providingadditional clearance to allow for manufacturing and assembly tolerancesand providing a further interior path for infiltration, flow andtransport of blood and fluids within the implant. Optionally, bottomclearance gaps 444 and 454 may be eliminated or made to an interferencefit condition to maximize structural integrity and surface to surfacecontact within the graft interior.

FIG. 4D shows side by side cross sectional views of two implantembodiments 460 and 470, with fully hydrated interference fits 463 and473, between hydrated chondroinductive portions 461 and 471 andosteoconductive portions 462 and 472, respectively.

FIGS. 5A-5D show a series of cross sectional views of a non taperedhydration controlled interference fit assembled implant. The crosssectional views of FIGS. 5A-5D preferably represent cross sections of acylindrical implant; but may alternatively represent extruded ormirrored sections producing rectilinear, slotted, triangular, square orpolygonal implants; or projected, swept or variable sections producingimplants of irregular or varying cross section.

FIG. 5A shows side by side cross sectional views of two implantembodiments, one with assembled cap pieces 501 and 502 mating with baseportion 503 to form a three piece assembly 500, and the other with amono cap portion 511 mating with base portion 513 to form a two pieceassembly 510. Bore 504 and bore 514 are adapted to mate with shaft 505and shaft 515, respectively. An optional hole 506 is provided as anadvantageous graft manipulation hole and as an additional conduit orchannel allowing access of blood and other fluids from the surgicalimplantation site into the implant interior. When the base material isporous, such as cancellous bone material, the optional hole 506 may bereplaced by a flat bottom 516 in the base portion 513, providingadditional strength and structural integrity.

FIG. 5B shows side by side cross sectional views of two implantembodiments 520 and 530, with dehydrated chondroinductive portions 521and 531 in position for assembly just above osteoconductive portions 522and 532, respectively. Dehydrated chondroinductive portions 521 and 531exhibit reduced diameter dimensions including shaft dimensions 523 and533, respectively, which are smaller than or substantially equal to boredimensions 524 and 534, respectively. For clarity and ease ofunderstanding, other shrinkage and warping effects such as the drawingin, curling, warping or curving of shafts 525 and 535, respectively, arenot shown.

FIG. 5C shows side by side cross sectional views of two implantembodiments 540 and 550, with an assembly of dehydrated chondroinductivecap portions 541 and 551 mated with osteoconductive base portions 542and 552, respectively. Dehydrated assembly clearance gaps 543 and 553,respectively, are visible around the shaft and bore fits of the twoimplant embodiments. Optional bottom clearance gaps 544 and 554,respectively, are visible in the assemblies, advantageously providingadditional clearance to allow for manufacturing and assembly tolerancesand providing a further interior path for infiltration, flow andtransport of blood and fluids within the implant. Optionally, bottomclearance gaps 544 and 554 may be eliminated or made to an interferencefit condition to maximize structural integrity and surface to surfacecontact within the graft interior.

FIG. 5D shows side by side cross sectional views of two implantembodiments 560 and 570, with fully hydrated interference fits 563 and573, between hydrated chondroinductive portions 561 and 571 andosteoconductive portions 562 and 572, respectively.

FIGS. 6A-6D show a series of cross sectional views of a non taperedundercut step or counter bore hydration controlled interference fitassembled implant. The cross sectional views of FIGS. 6A-6D preferablyrepresent cross sections of a cylindrical implant; but may alternativelyrepresent extruded or mirrored sections producing rectilinear, slotted,triangular, square or polygonal implants; or projected, swept orvariable sections producing implants of irregular or varying crosssection.

FIG. 6A shows side by side cross sectional views of two implantembodiments, one with assembled cap pieces 601 and 602 mating with baseportion 603 to form a three piece assembly 600, and the other with amono cap portion 611 mating with base portion 613 to form a two pieceassembly 610. Stepped bore 604 and stepped bore 614 are adapted to matewith stepped shaft 605 and stepped shaft 615, respectively. An optionalhole 606 is provided as an advantageous graft manipulation hole and asan additional conduit or channel allowing access of blood and otherfluids from the surgical implantation site into the implant interior.When the base material is porous, such as cancellous bone material, theoptional hole 606 may be replaced by a flat bottom 616 in the baseportion 613, providing additional strength and structural integrity.

FIG. 6B shows side by side cross sectional views of two implantembodiments 620 and 630, with dehydrated chondroinductive portions 621and 631 in position for assembly just above osteoconductive portions 622and 632, respectively. Dehydrated chondroinductive portions 621 and 631exhibit reduced diameter dimensions including shaft dimensions 623 and633, respectively, which are smaller than or substantially equal to boredimensions 624 and 634, respectively. For clarity and ease ofunderstanding, other shrinkage and warping effects such as the drawingin, curling, warping or curving of shafts 625 and 635, respectively, arenot shown.

FIG. 6C shows side by side cross sectional views of two implantembodiments 640 and 650, with an assembly of dehydrated chondroinductivecap portions 641 and 651 mated with osteoconductive base portions 642and 652, respectively. Dehydrated assembly clearance gaps 643 and 653,respectively, are visible around the shaft and bore fits of the twoimplant embodiments. Optional bottom clearance gaps 644 and 654,respectively, are visible in the assemblies, advantageously providingadditional clearance to allow for manufacturing and assembly tolerancesand providing a further interior path for infiltration, flow andtransport of blood and fluids within the implant. Optionally, bottomclearance gaps 644 and 654 may be eliminated or made to an interferencefit condition to maximize structural integrity and bone to bone contactwithin the graft interior.

FIG. 6D shows side by side cross sectional views of two implantembodiments 660 and 670, with fully hydrated interference fits 663 and673, between hydrated chondroinductive portions 661 and 671 andosteoconductive portions 662 and 672, respectively.

FIGS. 7A-7D show a series of cross sectional views of a negativelytapered stepped bore hydration controlled interference fit assembledimplant. The cross sectional views of FIGS. 7A-7D preferably representcross sections of a cylindrical implant; but may alternatively representextruded or mirrored sections producing rectilinear, slotted,triangular, square or polygonal implants; or projected, swept orvariable sections producing implants of irregular or varying crosssection

FIG. 7A shows side by side cross sectional views of two implantembodiments, one with assembled cap pieces 701 and 702 mating with baseportion 703 to form a three piece assembly 700, and the other with amono cap portion 711 mating with base portion 713 to form a two pieceassembly 710. Negatively tapered dual truncated bore 704 and negativelytapered dual truncated bore 714 are adapted to mate with negativelytapered dual truncated shaft 705 and negatively tapered dual truncatedshaft 715, respectively. Each of negatively tapered shaft 705,negatively tapered shaft 715, negatively tapered bore 704 and negativelytapered bore 714 is truncated top and bottom, preferably by a verticalchamfer 707 as shown, alternatively by a round, angled chamfer or othergeometric feature (not shown), to improve manufacturability, increasemanufacturing tolerances and increase physical robustness and breakageresistance of the implant, thus forming a negatively tapered dualtruncated hydration controlled interference fit implant. Truncations maybe adapted to a positively tapered or non-tapered shaft and bore fit aswell (not shown) and a single truncation may provide some of thebenefits of a dual truncation. An optional hole 706 is provided as anadvantageous graft manipulation hole and as an additional conduit orchannel allowing access of blood and other fluids from the surgicalimplantation site into the implant interior. When the base material isporous, such as cancellous bone material, the optional hole 706 may bereplaced by a flat bottom 716 in the base portion 713, providingadditional strength and structural integrity.

FIG. 7B shows side by side cross sectional views of two implantembodiments 720 and 730, with dehydrated chondroinductive portions 721and 731 in position for assembly just above osteoconductive portions 722and 732, respectively. Dehydrated chondroinductive portions 721 and 731exhibit reduced diameter dimensions including shaft dimensions 723 and733, respectively, which are smaller than or substantially equal to boredimensions 724 and 734, respectively. For clarity and ease ofunderstanding, other shrinkage and warping effects such as the drawingin, curling, warping or curving of shafts 725 and 735, respectively, arenot shown.

FIG. 7C shows side by side cross sectional views of two implantembodiments 740 and 750, with an assembly of dehydrated chondroinductivecap portions 741 and 751 mated with osteoconductive base portions 742and 752, respectively. Dehydrated assembly clearance gaps 743 and 753,respectively, are visible around the shaft and bore fits of the twoimplant embodiments. Optional bottom clearance gaps 744 and 754,respectively, are visible in the assemblies, advantageously providingadditional clearance to allow for manufacturing and assembly tolerancesand providing a further interior path for infiltration, flow andtransport of blood and fluids within the implant. Optionally, bottomclearance gaps 744 and 754 may be eliminated or made to an interferencefit condition to maximize structural integrity and surface to surfacecontact within the graft interior.

FIG. 7D shows side by side cross sectional views of two implantembodiments 760 and 770, with fully hydrated interference fits 763 and773, between hydrated chondroinductive portions 761 and 771 andosteoconductive portions 762 and 772, respectively.

FIGS. 8A-8D show top, perspective, section and side views, respectively,of an assembled implant 800. The chondroinductive cap diameter 801 issmaller than the osteoconductive base diameter 802. The osteoconductivebase height 804 is about one and one half times larger than thechondroinductive cap height 803. Assembled cap pieces 805 and 806 makeup cap portion 807 which mates with base portion 808 via interferencefit 809.

FIGS. 9A-9D show top, perspective, section and side views, respectively,of an assembled implant 900. The chondroinductive cap diameter 901 islarger than the osteoconductive base diameter 902. The osteoconductivebase height 904 is about one and one half times larger than thechondroinductive cap height 903. Assembled cap pieces 905 and 906 makeup cap portion 907 which mates with base portion 908 via interferencefit 909.

FIGS. 10A-10D show top, perspective, section and side views,respectively, of an assembled implant 1000. The chondroinductive capdiameter 1001 is substantially or about the same size as theosteoconductive base diameter 1002. The osteoconductive base height 1004is about one and one half times larger than the chondroinductive capheight 1003. Assembled cap pieces 1005 and 1006 make up cap portion 1007which mates with base portion 1008 via interference fit 1009.

FIG. 11A shows a perspective view of a chondroinductive washer portion1100.

FIGS. 11B-11F show a series of cross sectional views of severalembodiments of a two part upper washer and lower fixation portionimplant. Upper portion 1100 and lower portions 1101 to 1006 may each beformed of various materials including mineralized or demineralizedcortical or cancellous bone. Upper portions 1100 are preferably formedof demineralized cortical bone. Lower portions 1101 to 1106 arepreferably formed of mineralized cortical or cancellous bone, with thetop surface 1107 preferably demineralized or recessed below the upperportion 1100.

FIG. 11B shows a perspective view of a chondroinductive washer portion1100 together with a negatively tapered osteoconductive fixation portion1101. The fixation portion 1101 may be physically compressed, dehydratedor force fit into the surgical implantation site.

FIG. 11C shows a perspective view of a chondroinductive washer portion1100 together with a non-tapered osteoconductive fixation portion 1102.The fixation portion 1102 may be physically compressed, dehydrated orforce fit into the surgical implantation site.

FIG. 11D shows a perspective view of a chondroinductive washer portion1100 together with a positively tapered osteoconductive fixation portion1103. The fixation portion 1103 may be physically compressed, dehydratedor force fit into the surgical implantation site.

FIG. 11E shows a perspective view of a chondroinductive washer portion1100 together with a threaded osteoconductive fixation portion 1104. Thefixation portion 1104 may be threaded into and physically compressed,dehydrated or force fit into the surgical implantation site.

FIG. 11F shows a perspective view of a chondroinductive washer portion1100 together with a wedge portion 1105 and an expandableosteoconductive fixation portion 1106. The wedge portion 1105 forces theexpandable osteoconductive portion 1106 to expand when inserted.Expandable portion 1106 may have stress reliefs or slots 1107 cut at oneor more points around its circumference and along its length.

FIG. 12A shows a perspective view of a unitary chondroinductive anchoredcap implant 1200, with a chondroinductive top portion 1210 and anosteoconductive fixation portion 1220.

FIGS. 12B-12F show a series of cross sectional views of severalembodiments of a one part anchored cap implant. Upper portion 1210 andlower portions 1221 to 1226 may each be formed of various materialsincluding mineralized or demineralized cortical or cancellous bone.Upper portions 1210 are preferably formed of demineralized corticalbone. Lower portions 1221 to 1226 are preferably formed of mineralizedcortical or cancellous bone. A unitary implant having portions ofdifferent materials such as mineralized cancellous lower portion and ademineralized cortical upper portion is possible wherecortical-cancellous bone material is recovered from a specific anatomicsite having both cortical and cancellous bone present, such as an iliaccrest or femoral head, processed to preserve and align the naturalcortical-cancellous transition, and segmentally demineralized inselected regions or portions, such as a demineralized cortical upperportion.

FIG. 12B shows a cross sectional view of a unitary anchored cap implanthaving a chondroinductive portion 1210 together with a negativelytapered osteoconductive fixation portion 1221. The fixation portion 1221may be physically compressed, dehydrated or force fit into the surgicalimplantation site.

FIG. 12C shows a cross sectional view of a unitary anchored cap implanthaving a chondroinductive portion 1210 together with a non-taperedosteoconductive fixation portion 1222. The fixation portion 1222 may bephysically compressed, dehydrated or force fit into the surgicalimplantation site.

FIG. 12D shows a cross sectional view of a unitary anchored cap implanthaving a chondroinductive portion 1210 together with a positivelytapered osteoconductive fixation portion 1223. The fixation portion 1223may be physically compressed, dehydrated or force fit into the surgicalimplantation site.

FIG. 12E shows a cross sectional view of a unitary anchored cap implanthaving a chondroinductive portion 1210 together with a threadedosteoconductive fixation portion 1224. The fixation portion 1224 may bethreaded into and physically compressed, dehydrated or force fit intothe surgical implantation site. For clarity, the threaded surface isshown in full, non cross section view.

FIG. 12F shows a perspective view of a unitary anchored cap implanthaving a chondroinductive portion 1200 together with a wedge portion1225 and an expandable osteoconductive fixation portion 1226. The wedgeportion 1225 forces the expandable osteoconductive portion 1226 toexpand when inserted. Expandable portion 1226 may have stress reliefs orslots cut at one or more points around its circumference and along itslength (not shown).

FIG. 13A shows a perspective view of a chondroinductive washer implant1300 in a relaxed or undeformed state.

FIG. 13B shows a cross sectional view of implant 1300 in a bent ordeformed state and positioned above a surgically created defect 1301having undercut edge 1302 and extending from cartilage layer 1303,through cortical bone layer 1306 and into subchondral bone layer 1304.

FIG. 13C shows an implanted unitary undercut chondroinductive washerimplant 1300, including an undercut implant edge 1307 and a graftmanipulation or fixation hole 1305, implanted at a surgical defect site1301 and filling a cartilage layer 1303 and a subchondral bone layer1304 of defect 1301, while contacting or anchoring implant edge 1307 atleast in part beneath undercut edge 1302.

FIG. 14A shows a top view of a chondroinductive membrane implant 1400with pre-machined fixation holes 1401.

FIG. 14B shows a perspective view of a chondroinductive membrane implant1400 with pre-machined fixation holes 1401 which may be tapered throughpart or all of the thickness of the membrane.

FIG. 14C shows a section view of a chondroinductive membrane implant1400 with pre-machined fixation holes 1401 which may be tapered throughpart or all of the thickness of the membrane.

FIG. 14D shows a side view of a chondroinductive membrane implant 1400in a flat state. Chondroinductive membrane implant 1400 may optionallybe produced in a convex, concave or irregular shape (not shown) profileto fit the implant site.

FIGS. 15A-15C show a series of cross sectional views of an osteochondralsurgical site for a primary plug procedure (A) in the disease state, (B)after creation of the primary surgical defect or core, and (C) followingrepair with an implant, respectively, wherein one or more implants areimplanted by the present methods.

FIG. 15A shows a section view of an osteochondral defect 1503 at anosteochondral surgical site 1500, extending through a cartilage layer1501 and into a subchondral bone layer 1502. The thin cortical shellexisting between the cartilage layer and subchondral bone layer has beenomitted for clarity.

FIG. 15B shows a section view of a surgically created defect or core1504 extending through a cartilage layer 1501 and into a subchondralbone layer 1502, created by drilling or coring out of defect 1503 fromFIG. 15A.

FIG. 15C shows a section view of a bifunctional implant 1505, implantedin a surgically created defect or core 1504 extending through acartilage layer 1501 and into a subchondral bone layer 1502, created bydrilling or coring out of defect 1503 from FIG. 15A.

FIG. 15D shows a top or plan view of a first bifunctional implant 1505having an assembly seam 1506, implanted at an osteochondral defect site1500 and a second bifunctional implant 1507 implanted in a snowmanconfiguration, overlapping the first implant 1505 by about one third.The second implant 1507 is located along or in the direction of seam1506.

FIGS. 16A-16E show a series of section views of an osteochondralsurgical site 1600 for a secondary or backfill plug procedure with thedefect 1601 in the disease state, after creation of the primary surgicaldefect or core 1602, after creation of the secondary surgical defect1603 by removal of the secondary plug core 1604, following repair of theprimary defect 1602 with the secondary core 1604, and following repairof the secondary or backfill defect 1603 with a bifunctional implant1605, respectively, wherein one or more implants are implanted by thepresent methods.

FIG. 16A shows a section view of an osteochondral surgical site 1600 fora secondary or backfill plug procedure with the defect 1601 in thedisease state. The defect 1601 extends through the cartilage layer 1610and into the subchondral bone layer 1620.

FIG. 16B shows a section view of an osteochondral surgical site 1600after creation of the primary surgical defect or core 1602, extendingthrough the cartilage layer 1610 and into the bone layer 1620.

FIG. 16C shows a section view of an osteochondral surgical site 1600after creation of the secondary surgical defect 1603 by removal of thesecondary plug core 1604.

FIG. 16D shows a section view of an osteochondral surgical site 1600following repair of the primary defect 1602 with the secondary core1604, which was removed from the secondary or backfill 1603 defect inFIG. 16C.

FIG. 16E shows a section view of an osteochondral surgical site 1600following repair of the secondary or backfill defect 1603 with abifunctional implant 1605.

FIGS. 17A-17D show a series of orthogonal views and an explodedperspective view of a section of the shaft of a long bone 1700, showingthe location for recovery of a blank 1701 to produce a hemi cylindricalcortical bone portion 1702, advantageously producing an implant portionhaving naturally occurring internal Haversian canals 1703.

FIG. 17A shows a top plan view of a blank 1701 to produce a hemicylindrical cortical bone portion 1702.

FIG. 17B shows a right side view of a blank 1701 to produce a hemicylindrical cortical bone portion 1702, advantageously producing animplant portion having naturally occurring internal Haversian canals1703.

FIG. 17C shows a front view of a blank 1701 to produce a hemicylindrical cortical bone portion 1702, advantageously producing animplant portion having naturally occurring internal Haversian canals1703.

FIG. 17D shows an exploded perspective view of a blank 1701 to produce ahemi cylindrical cortical bone portion 1702, cut from a section of theshaft of a long bone 1700 in an axial alignment, advantageouslyproducing an implant portion having naturally occurring internalHaversian canals 1703 aligned with a major body axis of the implantportion 1702.

FIG. 18A shows a perspective view and FIG. 18B shows a perspective crosssection view of the condyle 1801 of a long bone 1800, wherein thecancellous bone source material is recovered, typically by sawing arectangular section 1802 with a saw 1803 along cut line 1804 and/or bycoring out a cylindrical section 1805 with a coring drill 1806,advantageously producing an implant having optimal density and qualityof cancellous bone for the formation of an osteoconductive base.

FIG. 19 shows a perspective cross sectional view of a cylindricalcartilage repair implant 1901 implanted at an osteochondral surgicalsite 1900 by the present methods. A surgically created defect 1902passes through a cartilage layer 1903 and into a subchondral bone layer1904 of the patient. A chondroinductive demineralized cortical bone capportion 1905 fills the top region of the surgical defect 1902 within thecartilage layer 1903. An osteoconductive cancellous bone base portion1906 fills the bottom region of the surgical defect 1902 within thesubchondral bone layer 1904. Base portion 1906 is assembled from twopieces 1906 a and 1906 b, which meet at seam 1906 c, visible through thecross section. A negatively tapered shaft and bore interference fitholds pieces 1906 a and 1906 b together with cap 1905. Natural Haversiancanals 1908 are substantially in alignment with the major axis ofimplant 1901 and in communication between base portion 1906 and topsurface 1909 of cap portion 1905.

In one embodiment the assembled implants include a chondroinductiveportion having a characteristic width or diameter which is substantiallythe same as a characteristic width or diameter of an osteoconductiveportion, providing for a uniform fit and easy insertion at aosteochondral defect site.

In another embodiment the assembled implants include a chondroinductiveportion having a characteristic width or diameter which is larger than acharacteristic width or diameter of a corresponding osteoconductiveportion, providing for an oversized chondroinductive portion and tightfit with the cartilage layer upon insertion at a osteochondral defectsite, such as a surgically created defect site.

In another embodiment the assembled implants include a chondroinductiveportion having a characteristic width or diameter which is smaller thana characteristic width or diameter of a corresponding osteoconductiveportion, providing for an oversized osteoconductive portion and tightfit with the subchondral bone layer upon insertion at an osteochondraldefect site. This oversized osteoconductive portion has the addedadvantage of insertion into the defect site without direct compressionof or damage to the chondroinductive portion.

In one embodiment, an assembly includes at least one osteoconductivecancellous xenograft bone portion and at least one chondroinductivecortical allograft bone portion. In an alternative embodiment, anassembly includes at least one osteoconductive cancellous allograft boneportion and at least one chondroinductive cortical xenograft boneportion. Preferably, the xenograft bone portion in either embodiment istreated to remove blood, fat, lipids, antigens, unattached proteins or acombination of these.

The present implants may optionally be provided with a secondchondroinductive portion which is adapted for insertion around theprimary implant at the osteochondral defect site. This secondchondroinductive portion may either be assembled or not assembled to theprimary implant prior to insertion, and having the same or differentproperties with respect to source material, mineralization, hydrationstate, or orientation of Haversian canals. This second chondroinductiveportion fits around the first chondroinductive portion and fills anypotential gap between the implant and the surrounding articularcartilage and provides for improved healing, remodeling and regenerationof the cartilage. This second chondroinductive portion may take the formof a concentric cylinder or partial cylinder around, on top of oroverlapping the first chondroinductive portion.

In an alternative embodiment of the implants of the present invention,an elongate cortical bone portion, preferably a cylindrical portion, istaken from a long bone, preferably from the diaphysis of a long bone, inan orientation resulting in substantial alignment between a major axisof the elongate cortical bone portion and the primary direction ororientation of the naturally occurring Haversian Canals in the longbone. This produces an elongate bone implant with canals oriented alongits length, substantially parallel to a major body axis of the implant.This all cortical implant is preferably of unitary construction andtaken from a single core or piece of bone. One end of the elongate orcylindrical cortical bone implant is then substantially demineralized toproduce a chondroinductive demineralized cortical bone portion. Theopposing end of the implant is maintained in a mineralized, lightlydemineralized, or partially demineralized state. The cortical bonestructure at this second end, either mineralized, lightly demineralizedor partially demineralized, provides an osteoconductive cortical boneportion. Alternatively, the opposing end of the implant is alsosubstantially demineralized, with the central region of the implantmaintained in a mineralized, lightly demineralized, or partiallydemineralized state.

In yet another alternative embodiment an elongate cortical bone portion,preferably a cylindrical portion, is taken from a long bone, preferablyfrom the diaphysis of a long bone, in an orientation resulting insubstantial alignment between a major axis of the elongate cortical boneportion and the primary direction or orientation of the naturallyoccurring Haversian Canals in the long bone. This produces an elongatebone implant with canals oriented along its length, substantiallyparallel to a major body axis of the implant. This all cortical implantis preferably of unitary construction and taken from a single core orpiece of bone. Most or all of the elongate or cylindrical cortical boneimplant is then substantially demineralized to produce achondroinductive demineralized cortical bone cartilage repair implant.

In one embodiment, an elongate cortical bone implant is provided havinga cylindrical, rectangular, elliptical, oval or egg shaped body withsides which are either rectilinear or arcuate, and may be convex,concave or substantially flat across all or a portion of their length.The implant of this embodiment is formed substantially from corticalbone, having a major body axis running along its length, and ispreferably recovered from the diaphysis of a long bone such that thenaturally occurring Haversian canals of the cortical bone material arein substantial alignment with a major body axis of the implant, and/orin communication with one or more end surfaces of the implant. The endsurfaces may be flat, concave or convex. The implant of this embodimentis typically demineralized at one end, alternatively demineralized atboth ends or along most or all of the entire length of the implant. Thedemineralization may vary along the length of the implant. For example,the implant may be substantially demineralized at a first end andpartially demineralized at a second end, with either a sharp transitionor a broad zone of transition between the substantially mineralized andpartially mineralized portions. Preferably, the implant is a unitaryimplant mineralized along one-half to two-thirds of its length anddemineralized along one-third to one-half of its length.

These unitary implants may have negatively tapered, non-tapered,positively tapered, threaded or expanding osteoconductive fixationportions that allow for fixation in the surgical site. Expandableportions may have stress reliefs or slots cut at one or more pointsaround their circumference and along their length. The fixation portionmay be physically compressed, threaded, dehydrated or force fit into thesurgical implantation site.

The present invention also provides a method of using an assembledcartilage repair implant to treat a cartilage defect in a mammal,including filling an osteochondral defect having a subchondral bonelayer and a cartilaginous layer with an assembled implant adapted forimplantation into a bone cartilage junction, wherein the assembledimplant has at least one osteoconductive cancellous bone portion and atleast one chondroinductive cortical bone portion. In this method thesubchondral bone layer of the defect is filled with the osteoconductiveportion and the cartilaginous layer of the defect is filled with thechondroinductive cortical bone portion.

The present disclosure also describes an assembled cartilage repairimplant, suitable for implantation at an osteochondral site in a humanpatient, and assembled via an interference fit, having at least oneosteoconductive cancellous bone portion and at least onechondroinductive demineralized cortical bone portion, wherein theosteoconductive portion and the chondroinductive portion are assembledin a stacked relationship. The hydration controlled interference fit ispreferred because it allows a solid connection between anosteoconductive base portion and an chondroinductive cap or top portion.A hydration controlled interference fit is especially preferred when thechondroinductive top portion is assembled from two or more pieces ofdemineralized cortical bone, because it can be configured to hold thetwo or more pieces together in alignment and prevent separation ordisplacement of the two or more pieces.

The present disclosure also describes an implant adapted forimplantation at an articulating cartilage site, with a chondroinductivemembrane of demineralized cortical bone, including natural canalsoriented across the thickness of the membrane and providing naturalporosity, at least one machined, formed or punched hole adapted toreceive a fixation device such as suture, a pin, a staple, or a bonepin, and a flat, smooth or convex upper surface, adapted to approximatethe surface geometry of an articulating cartilage site.

In an alternative embodiment, the membrane is recovered, preferably froma long bone, in a radial section wherein the Haversian canals areoriented at an oblique angle or transverse to the thickness of themembrane, typically running along either the length or width of themembrane, or both. In this alternative embodiment, membrane porosity canbe provided by perforations or holes drilled, punched, etched orotherwise formed across the thickness of the membrane, preferably afterdemineralization, to provide a chondroinductive membrane.

In another embodiment an implant adapted for implantation at anarticulating cartilage site is provided, having a membrane ofdemineralized cortical bone, including natural Haversian canals orientedacross the plane of the membrane. Natural Haversian canals orientedgenerally across or at substantial angle to the plane of the membranemay advantageously provide transport, signaling, and growth pathwaysacross the thickness of the membrane to support ingrowth,chondroinduction and chondroconduction.

A “membrane” is a flexible or semi-flexible matrix whose length,diameter and/or width is greater than its thickness, typically at leastabout 2 times greater, preferably at least about 5 times greater,alternatively at least about 10 times greater. A membrane may be used towithstand physiological loading and maintain structural support whileallowing or facilitating transport of specific cell or fluid types, suchas large or small cells, water or blood. A membrane may be secured byphysical fixation, by design of the surrounding implantation site, or bychemical or biological adhesives, glues or other chemical bondingagents. A membrane may be secured at one or more points near its centeror along its edges or both. A preferred embodiment is a membrane whichhas a thickness which is constant or varies across its length and width,within a range between about 0.5 mm and about 5 mm.

One embodiment of a membrane is a “washer”, typically secured by asingle means of physical fixation at or near its center, alternativelysecured by one or more fixation devices along its periphery. A washer istypically between about 4 mm and about 12 mm in width or diameter, ispreferably circular, and may be formed flat or concave or convex toapproximate the geometry of the intended implantation site.

An “anchored cap” implant is typically a unitary construct including achondroinductive cap portion and an osteoconductive anchoring portion.The cap portion is typically larger in diameter, length or width thanthe anchoring portion, preferably at least about 2 times larger,optionally at least about 4 times larger, also optionally at least about8 times larger. One embodiment of an anchored cap is preferably formedof cortical bone, and demineralized or partially demineralized in thechondroinductive cap region, optionally lightly demineralized, partiallydemineralized, or fully demineralized in the anchoring region. Anotherembodiment of an anchored cap is formed of a biocompatible polymer orother synthetic composition, optionally with the same or differentmaterial properties or composition in the cap region and anchoringregion. The anchoring region is typically deeper or longer than thethickness of the cap region, preferably at least about two times longer,optionally at least about 4 times longer, also optionally at least about8 times longer.

A “bifunctional implant” is one which is effective to provide twodifferent environments or supports for two types of tissue growth,regeneration, or repair. For example, a bifunctional implant may promotetwo types of tissue growth such as cartilage regeneration and boneregeneration adjacent to or at the same implant site. The bifunctionalimplant will typically have two distinct portions or regions.

An implant or portion is “osteoconductive” when it has the ability toserve as a scaffold to promote the growth or formation of bone, forminghealthy new bone tissue, bony tissue, or bone forming cells throughoutor along at least a portion of the scaffold.

An implant or portion is “osteoinductive” when it has the capacity tostimulate or promote the growth or formation of bone, forming healthynew bone tissue, bony tissue, or bone forming cells where such tissueotherwise would not form, such as by inducing the growth, maturation,reproduction or activity of stem cells, osteoblasts or any other cellsthat cause or contribute to the formation of bone.

In many of the embodiments described herein, certain elements aredescribed as osteoconductive, but other embodiments are alsocontemplated where like elements are osteoinductive instead of or inaddition to being osteoconductive.

“Cartilaginous tissues” include cartilage, articulating cartilage,hyaline cartilage, elastic cartilage, fibrocartilage and cartilage-liketissues.

An implant or portion is “chondroinductive” when it has the capacity tostimulate or promote the growth or formation of cartilaginous tissueswhere such tissue otherwise would not form, such as by inducing thegrowth, maturation, reproduction or activity of stem cells, fibroblasts,muscle cells or any other cells that cause or contribute to theformation of cartilaginous tissues.

An implant or portion is “chondroconductive” when it has the ability toserve as a scaffold to promote the growth or formation of cartilaginoustissues, such as by regeneration of cartilage or cartilage cells,forming new cartilaginous tissues, or cartilage forming cells throughoutor along at least a portion of the scaffold.

In many of the embodiments described herein, certain elements aredescribed as chondroinductive, but other embodiments are alsocontemplated where like elements are chondroconductive instead of or inaddition to being chondroinductive.

A “stacked relationship” means two or more pieces are arranged incontact with one another, such as where a first piece is at leastpartially on top of or disposed upon a second piece. A preferred stackedrelationship is where two pieces are in contact with one another in anaxial orientation with respect to a central axis of one of the pieces orof the combined assembly. In a simple form a stacked relationship existsbetween two or more substantially flat, rectangular, disk shaped, orplanar portions with a given thickness, arranged one on top of theother. In some cases a stacked relationship includes two or moreportions which overlap, interdigitate, protrude into, partially surroundor otherwise interact with each other. A child's building block set,where stacked pieces snap together through interlocking orinterdigitating features would be one example of such a stackedrelationship. A stacked relationship may include two or more stackedlayers. A “layer” may include one or multiple adjacent portions orpieces that make up that layer. The individual adjacent portions orpieces combine to form the layer, and each adjacent portion mayinterface with one or more portions in the next stacked layer. Geometricfeatures from a given portion in any layer may extend into other layers.A stacked relationship may also exist between 3 dimensional shapedportions with flat, ridged, toothed, textured, planar, non-planar,arcuate, non-arcuate, polyhedral, or other surfaces making up theinterface between any two portions.

Starting Materials and Procedures

Sources of material for the present implants include crosslinked ornon-crosslinked autograft, allograft, and xenograft bone; as well ascrosslinked cartilage, tendon, ligament, muscle, or other connectivetissue of autograft, allograft, or xenograft origin. Soft or connectivetissues, unlike bone tissues, are generally used in conjunction withother materials or otherwise processed to provide the levels of strengthand stiffness required by surgical constraints and anatomical remodelingprocesses. Sources of material for the present implants also includehydroxyapatite, tricalcium phosphate, calcium sulfate or other syntheticor natural calcium compounds, ceramics, other chemical compounds orpolymers known to approximate or mimic certain features of natural boneor cartilage, or to be biocompatible, bioabsorbable, or bioresorbable.

The present implants may be made from source material includingautograft bone, allograft bone, xenograft bone, or a combinationthereof. In some instances it is advantageous to provide an implantassembled from components having the same or different source materials.For example, allograft bone can be more chondroinductive than untreatedxenograft bone. In contrast, xenograft bone which has been treated toreduce inflammation and antigenicity may be equally or morechondroinductive as compared to allograft bone.

Allograft bone is advantageous for its lack of immune response, rapidincorporation and natural presence of growth factors encouragingosteoinduction or chondroinduction. Xenograft bone is advantageous forits availability, similarity to allograft bone, and for its greateravailability of larger sizes and certain geometric configurations.Autograft bone is advantageous for its lack of inflammation, possiblepresence of living cells, and rapid remodeling in the host. Autograftbone is less practical due to concerns over harvest-site morbidity,additional complication and costs associated with interoperative tissuerecovery, and logistical challenges for processing (for example,machining or sterilizing) in the operating room.

In some embodiments, materials for an assembled implant are selectedfrom different source materials. In assembled embodiments, differentmaterials are advantageously selected for individual components. In oneembodiment, a xenograft cancellous base provides an osteoconductivelower portion, while an allograft demineralized cortical bone capprovides a chondroinductive upper portion. Xenograft tissue is morereadily available, and when properly treated to remove or reduceantigenicity, may provide a structural osteoconductive matrix forremodeling. Allograft bone tissue contains a mix of naturally occurringgrowth factors in a collagen matrix to support chondroinduction andremodeling. In another embodiment, a hydroxyapatite base provides anosteoconductive lower portion, while an allograft demineralized corticalbone cap provides a chondroinductive upper portion. In anotherembodiment, a hydroxyapatite base provides an osteoconductive lowerportion, while a polymeric cap optionally seeded or provided with one ormore growth factors, cells or nutrients provides a chondroinductiveupper portion. In a particularly preferred embodiment an allograftmineralized cancellous base provides an osteoconductive lower portion,while an allograft demineralized cortical bone cap provides achondroinductive upper portion.

When the source material is a natural bone tissue such as autograft,allograft or xenograft bone, the selection of a specific type of bonetissue may be advantageous for a given application.

The demineralized cortical bone portions of the present implants may bemade up of from one to sixteen pieces of cortical bone, alternativelyfrom two to eight pieces of cortical bone, alternatively from two tofour pieces of cortical bone, preferably from one, two, or three piecesof cortical bone, more preferably from a single piece of cortical boneor from two pieces of cortical bone. A portion made up of two pieces ofcortical bone is advantageous because it provides optimal yield forintermediate to large implants, especially given the anatomicalconstraints of allograft tissue and limited availability with the properorientation of naturally occurring Haversian canals, along with arelatively simple mechanical design and assembly. A portion made up of asingle piece of cortical bone is advantageous because it providessimplicity, reliability, ease of manufacture and robustness in-situduring remodeling. A portion made up of one, two or three pieces ofcortical bone is advantageous because it provides a balanced andflexible set of options to produce suitable numbers of implants, withrelatively simple design and high reliability from the available bonesupply. A portion having from one to sixteen, two to eight, or two tofour pieces of cortical bone is desirable because it provides multipleoptions in the design and fabrication of suitable implants from theavailable bone supply, and especially from smaller bone pieces.

Cortical bone material taken from the central axial region or diaphysisof a long cortical bone naturally includes a series of canals, theseHaversian canals being oriented in a direction providing transport alongthe axial direction of the long bone. These natural constructs withinthe collagen matrix of the bone are well suited not only for transportof blood, cells and proteins, but also for cell proliferation andattachment critical to the early stages of either chondroinduction orosteoinduction. In one embodiment the present implants advantageouslyprovide cortical bone pieces or portions having internal canals,preferably the naturally occurring Haversian canals, specificallyoriented in a direction which provides transport between the outside ofthe graft or an outer surface of the cortical bone piece or portion, andthe inside of the graft or an inner surface of the cortical bone pieceor portion or to an interface of a cortical bone piece or portion and acancellous bone piece or portion. This is particularly preferred wherethe porous cancellous bone is intended for implantation at a preparedsurgical site in contact with the bloody surface of a preparedosteochondral defect providing blood, cells, nutrients, proteins and thelike to the implant. The orientation of the canals can advantageouslysupport and enhance the flow of blood, cells, nutrients, proteins andthe like into the cortical bone matrix to enhance chondroinduction.Alternatively, the canals are advantageously oriented to providetransport between any first surface of a piece or portion of corticalbone and any second surface of a piece or portion of cortical bone.

In one embodiment, cortical bone material is selected from a transversecut through the diaphysis of a long bone, such that the fiberorientation and the orientation of the Haversian canals within thecortical bone portion is aligned in a substantially perpendicularorientation with respect an outer face of the cortical bone portion. Inthis embodiment, the cortical bone portion is assembled to thecancellous bone portion such that in the final assembly the naturallyoccurring canals within the cortical bone portion are in communicationbetween an external surface of the cortical bone portion and an internalsurface of the cortical bone portion, wherein that internal surface ofthe cortical bone portion is in contact with an internal surface of thecancellous bone portion. Thus, the canals form a conduit or parallelseries of conduits from the outer surface of the cortical bone portion,to an inner surface of the cancellous bone portion. These conduits allowcells, blood, and nutrients from the host body to more readily reach theinterstices of the cortical bone portion after passing through theporous structure of the cancellous bone portion, thereby increasing theability of the cortical bone portion to remodel within the host afterimplantation, especially when the implant is placed into the recipientsuch that the cancellous portion is in contact with a prepared defectsite or vascularized bed of native cancellous or osteochondral tissue.

An alternative embodiment may be preferred when naturally occurringHaversian canals of the proper orientation are not available due to useof non-bone material, geometric or design constraints of the implant, oravailability of diaphysial cortical bone of the proper shape, size andorientation. In this alternative embodiment, canals are created in thecortical bone or non-bone material by techniques such as drilling,punching, etching, salt leaching, nano-fabrication or other suitablemethods. Surprisingly, it has been found that machining or drilling ofartificial canals prior to demineralization removes chondroinductivity,while machining or drilling of artificial canals after demineralizationactually maintains or promotes chondroinductivity. This is contrary tocommon practice and known methods of machining, where bone is usuallycut in a mineralized state to provide support and prevent damage to theunderlying collagen matrix and demineralized after machining. While theinventors do not intend to be bound by theory, it is thought thatheating or other changes during the machining of mineralized bone isdetrimental to growth factors and/or changes surface properties ofcollagen in a way which jeopardizes signaling events that stimulatechondrogenesis or chondroinductivity.

The source tissue can be treated, such as by demineralization. A bonetissue is fully mineralized when it has not been treated to remove anyof the naturally occurring mineral content, and thus contains about 100%of the naturally occurring residual calcium content by weight. A bonetissue is substantially mineralized when it contains at least about 90%residual calcium content by weight, alternatively at least about 95%,alternatively about 100%. Generally, a substantially mineralized bonestructure exhibits sufficient mechanical strength and dimensionalstability to withstand a press fit or interference fit in a surgicalimplantation site, and to allow remodeling without excessive subsidenceof the bone structure under anatomical loading conditions at a givensurgical site.

The desirable range for calcium content in the substantiallydemineralized bone may vary with specific application and geometry of agiven embodiment. Demineralization is typically achieved by an aciddriven reaction-front process, wherein the demineralization progressesin a “front” at a known uniform rate from all external surfacescontacted by the acidic medium. A uniform spherical bone portioncompletely submerged in excess acid will undergo a uniform and symmetricdemineralization as the reaction front moves at a constant rate inwardfrom the outer surface toward the center. An irregularly shaped boneportion, e.g., one with protrusions, channels or sharp corners, willhave thinner areas where the reaction fronts from opposing surfacescross over, completely demineralizing the thinner region, before thereaction fronts in thicker regions have completely demineralized thoseregions. This results in discrete regions of mineralized bone within apartially demineralized bone portion. These mineralized regions arehard, stiff, non-compliant, and may be more osteoinductive than thedemineralized regions surrounding them.

A bone tissue is lightly demineralized when 90% or more of its totalvolume remains mineralized. A bone tissue is partially demineralizedwhen between 90% and 10% of its total volume remains mineralized. A bonetissue is substantially demineralized when less than 10% of its totalvolume remains mineralized. For example, a substantially demineralizedbone has a mineralized volume that is less than about 5% total volume,preferably less than about 1%, more preferably less than about 0.1%,alternatively less than about 0.01%.

Generally, a substantially demineralized bone portion has a residualmineral content that does not noticeably impede the chondroinductivityof the implant, significantly obstruct the mechanics and load bearing ofthe implant in-situ, or unduly interfere with the manufacturing orsurgical implantation processes for that implant.

In making bone implants, cortical bone is often used in a mineralizedstate for its stiffness and structural properties. However, in makingthe present implants, substantially demineralized cortical bone ispreferred because it more closely approximates the physical propertiesof cartilage and because it is chondroinductive. In making boneimplants, mineralized or demineralized cancellous bone is often used asa non-structural filler material to provide a bone ingrowth path.However, in making the present implants, mineralized cancellous bone ispreferred as a structural graft element since it providesosteoconductivity in a matrix whose properties match that of the nativesubchondral bone.

When the source material includes hydroxyapatite, tricalcium phosphate,calcium sulfate or other synthetic or natural calcium compounds,implants may be formed by methods such as salt leaching and sintering.These materials have osteoconductive properties in certainconfigurations.

When the source material includes ceramics, other chemical compounds,synthetics or polymers known to approximate or mimic certain features ofnatural bone or to be biocompatible, bioabsorbable, or bioresorbable,suitable materials may include bioactive glass, PLA, PGA, PLLA, PGLA andother materials known to be suitable for human implantation.

Various materials will have different shrinkage and swellingcharacteristics. In some cases these material properties are known andpublished, while in other cases these material properties are determinedby laboratory measurement. The present methods can be applied even tomaterials having unusual material properties, such as materials whichshrink upon hydration or have very low or very high, highly anisotropic,or non-reversible ratios of shrinkage or swelling due to hydration ordehydration.

Material properties such as hydration related shrinkage and swelling areanisotropic in some materials, particularly those having a specificfiber or grain orientation such as that found in natural bone. Forexample, the shrinkage properties of a natural bone portion selectedfrom a long bone are greater across the radial direction of the longbone, and lesser across the axial direction.

Material properties such as hydration related shrinkage and swelling maybe altered by the condition or processing of the material. For example,bone can be made to have a higher degree of shrinkage or swelling byremoval of an amount of the natural calcium content through aciddemineralization or other methods.

Implant Design and Assembly

In some embodiments, the implants or a portion or piece of the implantshave a characteristic dimension, such as depth, thickness, width orlength. When an implant, portion or piece has a characteristicdimension, it has that dimension in a significant or relevant part ordegree, including but not limited to having that dimension uniformly(for example, a uniform depth, uniform thickness, uniform width oruniform length). Alternatively, a characteristic dimension is determinedfrom an average or weighted average across an area or volume, or alonganother dimension.

In some embodiments, the implants have a thickness or other dimensionwhich varies across their length and width. The thickness of the implantmay be optimized to approximate, be less than or exceed the depth of thearticulating cartilage layer or cartilaginous tissue layer, or toapproximate, be less than or exceed the overall depth of the surgicalimplantation site or surgically created defect. Typically the overallimplant thickness is within a range between about 0.3 mm and about 10mm, alternatively between about 0.5 mm and about 5 mm, preferablybetween about 1 mm and about 4 mm, also preferably between about 2 mmand about 3.5 mm.

In some embodiments of the present implants and methods, two or morecomponents are assembled together by interference fitting, such as byhydration controlled shrink fitting. “Hydration controlled interferencefit” refers to a condition where one or more of the geometric dimensionsof one or more portions are controlled at least in part by the additionor removal of moisture (usually water but possibly blood, saline oranother fluid) during the manufacturing or assembly process, to producean advantageous interference fit in the finished assembly orsub-assembly. In one example, a shaft is created on a first portion at asize which is nominally slightly larger than a corresponding bore in asecond portion, as measured in the hydrated state. Either one or both ofthe first and second portions are then dehydrated, wherein the resultingshrinkage of one or both portions produces a shaft which is slightlysmaller than the corresponding bore, as measured in the dehydratedstate. This is referred to as a clearance fit condition. The twoportions are easily assembled in the clearance fit condition. Followingassembly, the dehydrated portion(s) are fully hydrated to return them totheir hydrated dimensions and to form an interference fit. This isreferred to as an interference fit condition. In this way, aninterference fit is achieved without subjecting either portion to thestresses and deformations associated with a mechanical press fit, or theunwanted effects of thermal gradients required for a heat controlledinterference fit. The end result of assembly in a clearance fitcondition, followed by shrinkage and/or swelling, resulting in aninterference fit condition is a shrink fit.

A hydration controlled shrink fit is a type of hydration controlledinterference fit, and is particularly useful because it joins two piecestogether firmly, obtains a high degree of interference and exhibits lessdamage to and stress in the two assembled parts, as compared to a pressfit or other known methods of joining parts together.

Hydration controlled shrink fits and hydration controlled interferencefits are especially advantageous when working with materials which areporous, brittle, pliable or easily deformed during a press fitoperation. Bone, and especially demineralized bone material, isparticularly well suited to the present hydration controlledinterference fit assembly methods. Other materials such as bonesubstitutes, ceramics and polymers are also well suited to thesemethods. Some polymers, for example, have been shown to have comparablemechanical properties and pullout strength as compared to a cancellousbone material. Cancellous bone is the preferred material for the presentimplants due to its natural structure which facilitates osteoconduction,healing and remodeling.

The present methods are especially advantageous when assembling togethertwo or more pieces where the mating surface of a first piece is harder,more brittle or less compliant and the mating surface of a second pieceis softer, more pliable or easily deformed. When dissimilar materialsare assembled in a press fit, damage typically occurs to the softer ormore ductile of the two materials, resulting in reduced interference anda looser or less secure fit. The hydration controlled interference fitavoids this potential damage, resulting in a stronger or tighter fit andassembly. The hydration controlled interference fit is advantageous whenassembling any demineralized bone together with any mineralized bone,and especially advantageous when assembling demineralized cortical bonetogether with mineralized cancellous bone.

Alternatively, it is possible to combine elements of hydrationcontrolled shrink or interference fits together with other methods, suchas a more traditional press fit or thermally controlled interferencefit, to achieve a desired result. For example a shaft and bore press fitrequiring 0.15 mm nominal diametrical interference is modified orreplaced with a hydration controlled interference fit, allowing for 0.05mm actual interference during the dehydrated press fit assemblyoperation, but resulting in an effective interference of the desired0.15 mm interference following rehydration. This would subject thecomponents to considerably lower stresses and deformations during thepress fit assembly operation, while achieving a higher level ofinterference and tight fit in the final assembled implant.

The application of hydration controlled interference fit is dependentupon several factors, including mechanical design of each portion,material selection, material condition and orientation, order andselection of steps in the manufacturing and assembly process, andselection of suitable manufacturing methods.

Each portion must be given a mechanical design which will allow thehydration related shrinkage and swelling effects. Outside dimensionssuch as shaft diameters will generally shrink, while inside dimensionssuch as hole or bore dimensions will generally grow upon dehydration.Larger bodies generally have a greater total shrink, warp or distortionthan smaller bodies. However, smaller bodies may have a largerpercentage shrink, warp or distortion than larger bodies, especially ifthey have long, thin or irregular geometric features. Different specificeffects typically occur around sharp corners or complex geometricfeatures. Variances in dehydration shrinkage may result in significantwarpage or change of shape in a dehydrated body, however bodies willtypically return substantially to their original net shape uponrehydration. While it is contemplated that one or both parts of anassembly contribute to a hydration controlled interference fit, it isalso contemplated to mate one hydration swellable part to a secondnon-swellable part. For example, a demineralized cortical bone piececould be mated to a titanium piece to form a hydration controlledinterference fit.

In some preferred embodiments, parts are assembled from two differentsource materials, such as demineralized cortical allograft bone andmineralized cancellous allograft bone, in a shaft and bore fit. In theseembodiments the shaft is created on one component as a standingprotrusion or boss, and may be straight, positively tapered, ornegatively tapered. A positive taper results in a cone, frustoconical ortruncated cone protrusion. A negative taper results in tapered undercutor dovetail protrusion. The shaft and bore may also be stepped,providing a tapered or non-tapered undercut or locking feature. When thecorresponding bore is created with a positive taper, a tapered holeresults, mating with the truncated cone of a positively tapered shaft.When the corresponding bore is created with a negative taper, anundercut hole results, mating with the tapered undercut or dovetail of anegatively tapered shaft. When either the shaft or the bore is madewithout a taper, a straight cylindrical shaft or bore results. It iscontemplated to mix positively, negatively, or non-tapered shafts andbores to create a desired fit geometry for a hydration controlledinterference fit or shrink fit. A particularly preferred embodimentincludes the negatively tapered shaft and bore hydration controlledshrink fit.

Within shaft and bore fits, the shaft and the bore may have a round,oval, polygonal, irregular, flattened, keyed, or irregular shape. Insome embodiments a shaft of a first shape is mixed with a shaft of asecond shape. In a particular embodiment a round or cylindrical shafthas material removed from one side to produce a flattened shaft. Theflattened shaft then mates with a cylindrical bore, or optionally aflattened cylindrical bore, to produce a shaft and bore fit. This fithas the advantages of a single orientation for assembly and resistanceto rotation from that orientation. In another specific embodiment apolygonal shaft is provided to mate with a cylindrical bore. Thisembodiment has the advantages of controlled and focused stressdistribution and greater tolerance for variances in manufacturing orshrinkage processes. In a preferred embodiment a cylindrical shaft mateswith a cylindrical bore, with both shaft and bore optionally tapered,concentrically joining two cylindrical pieces together. This embodimenthas the advantage of ease of manufacture and assembly, no stressconcentrations, and no requirements for angular or rotational alignmentduring assembly or in use. In all shaft and bore fits, it iscontemplated that either the shaft or the bore may be assembled from twoor more pieces to form a larger portion or segment.

Similar to the shaft and bore fits, protrusion and slot fits are anothertype of fit that may be employed instead of or in combination with ahydration controlled interference fit or shrink fit, formed by providinga raised boss or protrusion on one piece for assembly with a cut slot orkeyway on a mating piece. Protrusion and slot fits may be straight,positively tapered, or negatively tapered, with constant or varyingprofiles which are rectilinear, arcuate, irregular, or any combinationof these in cross section.

Multiple fits of any kind are contemplated for use within a singleassembled implant. In one embodiment two oval shaft and bore fitsprovide redundancy and alignment to a cylindrical implant. In anotherembodiment an array of two or more protrusion and slot fits provideprecise alignment and orientation of two parts of an assembled implant.

The order and selection of steps in the manufacturing process isimportant to the successful use of hydration controlled interferencefit. Some features such as aligned holes or surfaces are preferablycreated prior to a change in hydration state to preserve uniformity ofcritical dimensions across a portion or across a finished graft. In somecases it is advantageous to cut in the wet or hydrated state, assemblein the dry or dehydrated state, and then cut other features afterassembly and swelling, with the whole graft in the hydrated state. Inother cases, it is more efficient or reliable from the perspective ofmanufacturing flow to perform all machining steps during a singleepisode, then perform assembly and hydration in a second episode.Certain features such as outer profiles spanning two or more portionsare preferably cut after assembly and rehydration to produce a reliablefinish in the final implant.

Alternatively, in one preferred embodiment using natural bone materialswith well understood material properties, two pieces are made separatelyand assembled in a later operation. In this embodiment, a mineralizedcortical bone portion is machined to shape in a hydrated state,including a tapered undercut shaft cut to final dimensions which willproduce the desired interference fit. This cortical bone portion is thendemineralized and sterilized in a single procedure, all in a hydratedstate. Following demineralization, the demineralized, sterilized portionof machined cortical bone is dehydrated under forced air flow, or byother suitable processes such as lyophilization. In a separate series ofoperations, a portion of mineralized cancellous bone is machined toshape in a hydrated state, including a tapered undercut bore cut todimensions which will produce the desired interference fit, thensterilized. Following sterilization of the mineralized, sterilizedportion of machined cancellous bone, the two bone portions are broughttogether for assembly, hydration and final packaging. The portions areassembled together with a clearance fit condition with the demineralizedcortical bone in the dehydrated state, then the entire assembly is fullyrehydrated resulting in a hydration controlled interference fit. In anoptional variation of this preferred embodiment one of the boneportions, such as the cortical bone portion, is processed from twosmaller equal pieces, with each of the two pieces making up about onehalf of the desired cortical bone portion including the tapered undercutshaft. This optional preferred embodiment has the advantage of makingmore bone material available for use by reducing the minimum size pieceof bone suitable as a starting material.

In a preferred embodiment of the method of making the implants thecortical bone material is machined to shape in a hydrated state, thendemineralized after machining by an aqueous or non-aqueous aciddemineralization process, then dehydrated by forced air flow,lyophilization or other suitable method of dehydration, prior to finalpackaging and terminal sterilization in a package of two or more layerssuitable for use in a surgical operating environment.

Lyophilization can be done with a lyophilizing machine until the bone issubstantially free of moisture. Forced air drying can be done with anysuitable source, such as a filtered, conditioned, sterile air supplyfound in many clean room environments. Lyophilization or forced airdrying volatilizes residual processing chemicals, produces a more stableintermediate for storage and handling in-process, and followspharmaceutical industry processing standards. Typically lyophilizationresults in a residual moisture content of about 10 weight percent orless, alternatively about 6 weight percent or less, alternatively about3 weight percent or less, alternatively about 2 weight percent or less,alternatively about 1 weight percent or less.

Alternatively, bone is dried until a functional test condition is met,such as a reduction in dimension or an ability to fit into a certainhole, mating piece or test gage. For example, a bone portion having ashaft may be dried under forced air until such time as it will readilyengage a mating piece having a bore under light hand pressure. Dryingunder forced air may be calibrated by time to dry, which variesaccording to temperature, relative humidity, and air flow rate. Typicaldrying times for some embodiments of the present implant portions may beat least about 30 minutes, preferably at least about 1 hour, morepreferably about 60 to 90 minutes, also typically about 1 to 2 hours,alternatively more than about 2 hours. Actual drying times may be longeror shorter depending on implant portion design, processing conditionsand airflow properties. Individual measurements or range limits may becombined to form new ranges. After the bone is dried, it can be storedin a manner that prevents rehydration from air moisture.

It is contemplated that the implants or assemblies are created outsidethe body of the intended recipient. This assembly outside the body hasseveral advantages. The manufacturing process is separated from thesurgical procedure, allowing for reduced cost and increased mechanismsfor quality assurance and process control, thus resulting in safer, moreeconomical and more reliable production of high quality grafts. Themanufacturing process can be conducted using materials and equipmentwhich may not be available or practical for use in the operating roomenvironment. For example, it would be impractical if not impossible tocompletely dehydrate or demineralize an implant portion during a singleoperation to produce a graft suitable for implantation into thatpatient.

In an alternative embodiment, it is contemplated that the implants orassemblies are created in part outside the body of the intendedrecipient and prior to the surgical implantation, but fully realized orfinalized during the surgical procedure or inside the body of therecipient. In one embodiment an implant is provided having a dehydrateddemineralized cortical bone chondroinductive upper portion and amineralized dehydrated cortical bone osteoconductive lower portion. Theimplant is delivered to the operating room in a sterile condition andfree of any residual blood or lipids, in a kit including sterilepackaging and instructions for use. The kit also optionally includes aninsertion device compatible with arthroscopic or minimally invasivesurgical technique. When this dehydrated implant is placed into thesurgically created defect at the site in need of repair, the patient'sown blood is drawn into the implant, rehydrating and swelling it whiledelivering native cells, nutrients and growth factors to supportchondroinduction and healing. The implant is optionally further hydratedby directed application of blood, sterile water, or saline prior toimplantation, or following implantation. The swelling action adds to anyoptional press fit or other fixation features and locks the lowerportion in place, preferably within the patient's subchondral bone, atthe surgically created defect site.

The use of appropriate manufacturing methods in the manufacturingprocess is important to the successful use of hydration controlledinterference fit. In certain materials, such as bone, wet machining orcutting in the hydrated state, with or without the presence of excessliquid is preferred since bone is typically recovered and processed in ahydrated state and since wet or hydrated bone has natural lubricitywhich results in less chipping or breakage of the bone and improvedsurface finish condition. The natural lubricity of bone and therelatively moderate feed rates and spindle or cutter speeds employed inthe machining of bone generally make additional lubricants or coolingfluids unnecessary, although sterile water, alcohol or saline may beused to remove debris from or to facilitate assembly of machined parts.

Dimensional changes due to changes in hydration state must be taken intoaccount when machining bone. For this reason it is preferable in somecases to dry machine bone which will be assembled or shipped in a freezedried or dehydrated state. The present implants are preferably storedand shipped in a hydrated state whenever a hydration controlledinterference fit is employed.

An implant is chondroinductive when it induces the growth or formationof cartilage or other cartilaginous tissue. Factors known to contributeto chondroinductivity include presence of growth factors such astransforming growth factor-beta (TGF-beta), insulin-like growth factor(IGF), cartilage-derived morphogenetic proteins (CDMPs), and bonemorphogenic proteins (BMPs). Additional factors contributing tochondroinductivity include cyclic compressive loading, hypoxicenvironment, surfaces that favor spherical as opposed to flattened cellconfiguration or surfaces that favor high cell density.

In some preferred embodiments, the chondroinductive implants exhibitstiffness and compliance similar to that found in natural articulatingcartilage, and/or have the presence of some amount of chondroinductivegrowth factors, and/or have an internal structure and micro-structure ofor similar to collagen which is supportive of cell migration, ingrowthand attachment, and/or have physical features such as canals or conduitswhich enhance or add mechanisms for cell, blood and fluid transport.

The static structural modulus (Young's Modulus) or stiffness ofcartilage has been reported between about 0.5 MPa and 1 MPa. Thestiffness of mineralized cortical bone is a highly anisotropic property,but has been reported between about 4 GPa and about 20 GPa.Demineralized bone matrix (DBM) pastes, gels or putties exhibitstiffness in the range of 0.1 MPa or less. In some preferredembodiments, the present implants comprise demineralized cortical bonematerial having a stiffness not more than about 1 GPa, alternatively notmore than about 500 MPa, alternatively not more than about 100 MPa,alternatively not more than about 50 MPa, alternatively not more thanabout 10 MPa, alternatively not more than about 5 MPa, alternatively notmore than about 2.5 MPa, alternatively not more than about 1.5 MPa,alternatively not more than about 1.0 MPa, alternatively not more thanabout 0.9 MPa, alternatively not more than about 0.8 MPa. Alternativelyor additionally, the present implants comprise demineralized corticalbone material having a stiffness at least about 0.2 MPa, alternativelyat least about 0.3 MPa, alternatively at least about 0.4 MPa, at leastabout 0.5 MPa, alternatively at least about 1 MPa, alternatively atleast about 5 MPa, alternatively at least about 10 MPa, alternatively atleast about 50 MPa, alternatively at least about 100 MPa, alternativelyat least about 0.5 GPa. Any of the foregoing maximum and minimumstiffness values can be combined to form a range, so long as the maximumis greater than the minimum. For example, the present implants maycomprise demineralized cortical bone material having a stiffness in therange between about 0.2 MPa and about 1 MPa, or even more preferably inone of the ranges between about 0.4 MPa and about 0.8 MPa, between about0.5 MPa and about 1 MPa, between about 0.5 MPa and about 0.7 MPa, orbetween about 0.3 MPa and about 0.9 MPa. Thus the demineralized corticalbone material used in certain preferred embodiments of the presentimplants has a stiffness within the range of that known for nativecartilage, while DBM pastes have a stiffness at least about one order ofmagnitude less than that found in native cartilage, and mineralizedcortical bone has a stiffness at least about 4 orders of magnitudegreater than that found in native cartilage.

The elastic modulus of mineralized cancellous bone, such as that foundin the subchondral bone layer and as preferred for the osteoconductivebase material of the present implants, is between about 2 GPa and about4 GPa, typically about 3 GPa.

The chondroinductive implants have the capacity to stimulate or promotethe formation of cartilage where such tissue otherwise would not form,such as by inducing the growth, maturation, reproduction or activity ofchondrocytes, stem cells, fibroblasts, muscle cells or any other cellsthan cause or contribute to the formation of cartilage, thereby formingcartilaginous tissue. Due to the many diverse factors influencingchondroinductivity, the presence or absence of a single factor is notdefinitively predictive of chondroinductivity in-vivo. For example,isolated TGF-beta may be chondroinductive under a first set ofconditions in-vivo or in-vitro, but may actually be non-inductive orosteoinductive under a second set of conditions in-vivo or in-vitro. Theacceptable measure of chondroinductivity of an implant is an in-vivomodel where the sample is implanted in an environment that does notspontaneously make cartilage, such as subcutaneously or in the abdomenmuscle preferentially in the small size animals, like mice, rats orrabbits, Urist, M. R., “Bone: Formation by Autoinduction,” Science160:893-894 (1965). The chondroinductivity of the sample can then beassessed via histological and other analysis of the extent of cartilageformation in the in-vivo model.

The present implants differ in several important aspects from implantsknown for other purposes. When the implants include demineralizedcortical bone as a chondroinductive element, the cortical bone elementis demineralized sufficiently to prevent damage to adjacent articularcartilage surfaces and to allow natural bearing and dispersion of forcesunder anatomical loading conditions.

Embodiments of the present implants differ from known assembled bonegrafts used in the spinal fusion implant or sports medicine and tendonfixation fields, where mineralized, lightly demineralized, or surfacedemineralized cortical bone constructs are used as osteoconductive orosteoinductive structural load bearing members. The preferredembodiments of the present implants have a relatively higher degree ofdemineralization and resulting lower modulus of elasticity and yieldstrength than spinal fusion implants or tendon fixation implants. Knownimplants for spinal fusion and tendon fixation would not serve asosteochondral implants, given their stiffness, roughness, and lack ofcompliance due to residual, substantial or total mineralization of thecortical bone elements.

Also in contrast to the present implants, demineralized bone matrix(DBM), as used in orthopedic applications, refers to a bone powder whichis demineralized and mixed with graft material or a carrier such asgelatin, glycerol or a biocompatible polymer to form a non-load-bearingpaste or putty composition. These DBM pastes differ from theosteochondral implants in the lack of ability of the DBM pastes tosupport anatomical loading in the joint space, their lack of ability tohold a preconfigured shape and/or maintain an assembly, and their lackof ability to support tissue regeneration in-vivo.

Synthetics, calcium compounds, ceramics, and polymers known in the artfor use in other implants can be included in the present implants butare generally non-preferred due to their inferior regenerative andremodeling properties as compared to the preferred embodiments of thepresent implants, their lack of naturally occurring growth factors, andtheir inability to remodel into living tissues such as articularcartilage and subchondral bone. Although synthetics, calcium compounds,ceramics, and polymers may have growth factors or other agents added tothem to promote chondroinductivity, the addition of a single growthfactor or a small number of agents with demonstrated in-vitrochondroinductivity may not reliably produce chondroinductivity in-vivo.

Example 1

This example demonstrates a method of making an embodiment of anassembled implant.

Cancellous bone was obtained from the condyles of long bones, oroptionally from the Talus or heel bone. The bone was cut into blankswith diameters ranging from roughly 6-13 mm and heights from 8-10 mmusing a band saw and coring tools. The inner geometry of the cancellousbone was then machined using a dovetail cutter. A 1.5 mm hole wasmachined in the bottom center of the 8 mm and 10 mm cancellous boneportions. The cancellous bone portions are measured, inspected forquality, packaged, and stored frozen until processing for sterilization.The cancellous bone portions were sterilized, defatted anddeantigenized, and soluble protein was removed by subjecting thecancellous tissue to cyclically alternating cycles of pressure andvacuum in the sequential presence of mild sterilizing chemicalsolutions. Following sterilization, the cancellous bone portions werepackaged and stored until assembly with the cortical bone pieces orportions.

Cortical bone from a long bone shaft was cut into planks using a bandsaw. Bone planks were then cut into rectangular bone blanks measuringroughly 7-10 mm in height, 7-14 mm in width, and 7-8 mm in length usinga band saw. Each blank was then machined to final dimensions such thatthe cortical bone portions have cap features with radii and negativelytapered shaft features with dovetails. The machined cortical boneportions were measured, inspected for quality, packaged, and storeduntil demineralization.

The surfaces of the cortical bone portions were decontaminated thenthoroughly rinsed with water and demineralized by immersing them in USPHydrochloric Acid (HCl), 1.0N (Thermo-Fisher) at an HCl volume toproduct volume ratio of at least 50:1. The container with corticalportions and acid was placed on a shaker and agitated. The cortical boneportions were then rinsed with phosphate buffered saline and then withwater.

After the final water rinse, the cortical bone portions were ready to beassembled with the cancellous portions. The cortical bone portions weredehydrated by placing under forced air flow. The 8 mm portions weredehydrated for about 45 minutes, the 6 mm portions for about 60 minutesand the 10 mm portions for about 85 minutes, or until the corticalportions become small enough to fit inside the mating cancellousportion. The shaft of the single cortical bone portion (6 mm) or thecombined assembled shafts of the two cortical bone portions (8 mm and 10mm) were placed into the bore of the cancellous portion and theassembled implant was placed into a fixture designed to hold implantsduring rehydration. The implants were rehydrated using water for about45 minutes or until the original cortical bone portion size andappearance had been restored. At this point, the implants were inspectedfor quality, packaged, and terminally sterilized.

Example 2

This example documents an animal study completed to confirm thechondroinductivity of an implant.

Prototype implants were implanted into an ectopic site in an athymicnude rat model, resulting in histologic evidence of chondroinductionwithout any signs of an inflammatory response.

Specifically, a 4 mm diameter by 2 mm tall disc taken from thedemineralized cortical bone portion of Example 1 was implanted inabdominal muscle pouches of athymic nude rats using a modified Uristmodel, Urist, M. R., “Bone: Formation by Autoinduction,” Science160:893-894 (1965). The explants were retrieved two weeks later,processed, and evaluated histologically for evidence of new cartilageformation. The control implants made from chemically inactivateddemineralized cortical bone material formed only fibrous material withinthe Haversian canals with minimal evidence of inflammation. Moresignificantly, the implants made from active demineralized cortical bonedemonstrated signs of chondrogenesis or new cartilage formation withminimal evidence of inflammation. Hence, the demineralized cortical bonematrix of the present invention provided both signaling and scaffoldingfor colonization by native restorative cells and the laying down of newcartilage.

Example 3

This example documents a cadaver study completed by a practicing surgeonexperienced in cartilage repair at an orthopedic clinic to confirm theproper function and methods of use for the present implants.

Several primary-site implants were made to production specificationsusing an assembled biological implant comprising a two piecechondroinductive demineralized cortical bone cap assembled via ahydration controlled interference fit to a mineralized cancellous boneosteoconductive portion. The assembled implants were implanted into acadaver knee using an open approach. The implants were left out at roomtemperature for several minutes and were then placed in room temperaturesaline for a minimum of ten minutes to ensure consistent final levels ofhydration prior to implantation. The surgeon prepared the implantationsite by coring out an 8 mm diameter plug from the primary site using anOATS single-use kit. He measured the depth of the defect using the depthgauge and verified that it was between 9 mm and 10 mm, as the plugheight is 10 mm. He then loaded the assembled implant into the 8 mmdiameter delivery tube such that the cancellous portion of the implantwas toward the bottom (so it would fill the cancellous portion of thedefect) and the demineralized bone portion was on the top (so it wouldbe congruent with the articulating surface). He aligned the deliverytube with the defect site and tamped the implant into the void. Theimplant was almost completely implanted, and at this point he removedthe delivery tube and completed pushing the implant into the site usinga surgical tamp and mallet. Once the implant was flush with thearticulating surface, the implantation was complete.

The surgeon then proceeded to implant a 10 mm implant in the samefashion, followed by a 6 mm implant in a “snowman” configuration withthe 10 mm implant. This was achieved by coring out a second 6 mm defectthat overlapped with ⅓ of the first installed 10 mm implant, resultingin an overlapping, non-coaxial, non-uniformly sized multiple implantconfiguration resembling the profile of a snowman. After coring the 6 mmdefect, he inserted the 6 mm implant using the delivery tube. The 10 mmimplant was slightly more depressed than the 6 mm implant in its finalposition, which was a result of the second implant pushing it down as itwas implanted. It was recommended that when using the snowman technique,the first implant be inserted to a depth of only about 8 to 8.5 mm sothat it has room to subside during implantation of the second implant.

The final implantation was a 10 mm implant into a widened 8 mm defect.This was done to determine robustness of the implant to situations wherean 8 mm defect was widened during surgery to the extent that the 8 mmimplant would no longer fill the void. The 10 mm implant fit well intothe widened 8 mm hole.

Example 4

This example documents a cadaver study to confirm the proper functionand methods of use for several implants.

Eighteen assembled bifunctional biological implants were evaluated in asimulated use environment to validate the design against user needs.

Primary site and backfill implants, sizes 6 mm, 8 mm, and 10 mm, wereevaluated by implanting into a cadaver knee using an open,non-arthroscopic technique.

Prior to implantation, the interface of the implants with theirappropriate delivery devices was evaluated. The implants were placedinto the instruments and each instrument was held vertically so that theend with the implant was facing upwards. The instrument was inverted sothat the implant end was facing the floor. This was repeated five timesto demonstrate that the implants do not fall out of the instrumentduring normal movement. In addition, the plungers for the instrumentswere used to push the implants out of the tube, as would be done duringimplantation. The implants did not become stuck in the tube. These testsdemonstrated that the implant's outer diameter dimensions are sufficientto interface with the appropriate instrumentation.

The implant was then evaluated to determine whether it was robust enoughto maintain integrity during typical manipulations. The cancellous endof the implant was trimmed 2 mm as might be done prior to implantationif the surgeon cored out a shallow defect. The implants did not crack,chip, break, or come apart, demonstrating that they could withstandnormal manipulations.

To prepare for the implantation, primary and backfill sites wereprepared by coring out appropriately sized defects using an OATSsingle-use kit. One defect of each primary size was cored on the primarysites of each femoral condyle, and one defect of each backfill size wascored on the edges of the condyles, which are typical sites forobtaining autologous plugs. The depth of each defect was measured usingthe depth gauge and it was verified that each was between 9 mm and 10mm. The implants were loaded into the delivery devices such that thecancellous portion of the implants were toward the bottom (so they wouldfill the cancellous portion of the defect) and the demineralized boneportion was on the top (so they would be congruent with the articulatingsurface). For each implantation, the delivery tube was aligned with thedefect site and tamped into the void. Tamping continued until theimplants were flush with the articulating surface.

After implantations were complete, the implants were inspected forintegrity. The articulating surfaces of the implants were in theiroriginal conformations and without chips or cracks. The demineralizedbone portions were firmly attached to the cancellous portions.

The performance of the implanted implants was evaluated by marking theposition of the implants and then manually cycling the knees from 90°flexion to full extension at a rate of about two cycles per second. Theknees were cycled 30 times. After cycling, the implants were examined.None had rotated or moved vertically out of position.

Example 5

This example demonstrates a method of using an embodiment of anassembled bifunctional biological implant for backfilling a secondarysite created during an autograft cartilage repair procedure in a humanpatient (e.g. OATS procedure).

The primary site lesion is identified and cored or drilled out usingappropriate instrumentation. A similarly-sized autograft cartilage plugis cored out from a relatively non load-bearing area of the same condyleusing appropriate instrumentation. The autograft plug is then insertedinto the void at the primary site.

The result from obtaining the autograft plug is a cylindrical void orsurgically created defect in the cartilage and underlying bone. Thedepth of the void is measured using a depth gauge. The depth gaugeserves to measure depth as well as compact any debris in the void. Thedepth of the void is made to be approximately 9-10 mm, and preferablyabout 9.8 mm for insertion of a 10 mm graft. The slightly undersizeddepth allows for compaction and reduction of any voids at the base ofthe implant while resulting in a flush and not recessed final height ofthe implant. An assembled implant with a similar diameter to the void ischosen. The graft is loaded into a delivery device (tube with an innerdiameter that is similar to the diameter of the graft) such thatfollowing placement the cancellous portion will fill the bottom of thevoid and the demineralized portion will be visible on the surface of thecondyle. The end of the tube holding the graft is aligned with and matedto the void. A rod with a similar diameter as the graft is inserted intothe tube and tamped against the graft using a surgical mallet, pushingthe graft into place. The rod may be tamped with force to push the graftinto position. When all of the cancellous portion and at least half ofthe demineralized portion of the graft are implanted, the tube and rodare removed. The graft is pushed further into the void using a standardsurgical tamp and mallet. Once the graft is flush with the surface andno protrusions remain, the implantation is complete.

Example 6

This example demonstrates a method of using an embodiment of anassembled bifunctional biological implant for repairing a primary sitedefect in a human patient.

The primary site lesion is identified and cored or drilled out usingappropriate instrumentation. The depth of the resulting void is measuredusing a depth gauge. The depth gauge serves to measure depth as well ascompact any debris in the void. The depth of the void is made to beapproximately 9-10 mm. An assembled implant with a similar diameter tothe void is chosen. The implant may be the same size as the void,slightly undersized or slightly oversized in either height or diameter,depending on surgeon preference. Typically the implant is slightlyoversized in both height and diameter for the void it is filling,resulting in a light press fit and slight compaction of the implant uponfull depth insertion. The implant is loaded into a delivery device (tubewith an inner diameter that is similar to the diameter of the implant)such that upon insertion the cancellous portion will fill the bottom ofthe void and the demineralized portion will be visible on the surface.The end of the tube holding the implant is aligned with and mated to thevoid. A rod with a similar diameter as the implant is inserted into thetube and tamped against the implant using a surgical mallet, pushing theimplant into place. The rod may be tamped with force to push the implantinto position. When all of the cancellous portion and at least half ofthe demineralized portion of the implant are implanted, the tube and rodare removed. The implant is pushed further into the void using astandard surgical tamp and mallet. Once the implant is flush with thesurface and no protrusions remain, the implantation is complete.

Example 7

This example demonstrates a surgical technique guide for a method ofusing an embodiment of an assembled bifunctional biological implant forrepairing a primary site defect in a human patient.

Identify the primary site lesion and remove damaged cartilage and debrisuntil the edges of the defect site are composed of healthy cartilage.

Determine the size of the lesion and decide how many assembled implantswill be needed and in what sizes. If multiple implants are needed,decide whether the implants will be placed next to one another oroverlapping. Plan to overlap implants by no more than ⅓.

Remove the implants from the packaging and allow to them to hydrate inroom temperature water or saline.

Using appropriate instrumentation, core or drill the defect using 6 mm,8 mm, or 10 mm diameter instruments. Use the smallest diameter possiblethat removes all damaged cartilage.

Measure the depth of the cored defect using a depth gauge. Use the depthgauge to compress debris at the bottom of the defect. Ensure that thedefect is 9.0-9.8 mm deep and that the bottom of the defect is parallelwith the surface of the articulating cartilage. If the defect is tooshallow, deepen the site by impacting the depth gauge with a mallet. Ifthe defect site is too deep, add cancellous bone from the coredmaterial.

Place the assembled implant into the delivery device such that thecancellous portion is visible on the implanting end of the tube. Thisresults in the cancellous portion being implanted at the bottom of thesite (congruent with the native cancellous) and the demineralizedcortical bone remaining at the surface of the defect (congruent withnative cartilage).

Align the opening of the delivery device with the defect. Guide theimplant into the defect by pushing on the rod. When the implant does noteasily slide into the defect site, use a mallet to impact the rod,pushing the implant into position. Ensure that the delivery deviceremains perpendicular to the surface of the articulating cartilage toavoid widening the defect site or implanting the implant at an angle.

Once all of the cancellous portion is implanted and at least about halfof the demineralized bone portion is implanted below the articulatingcartilage surface, the delivery tube may be removed (if desired) and thewide end of the delivery device or a surgical tamp and mallet may beused directly on the surface of the implant. Impact the surface of theimplant until it is completely flush with the surface of thearticulating cartilage. Do not leave portions of the implant protrudingabove the surface.

If additional implants are needed and are going to be implanted next toone another, a similar technique as for the first implant should befollowed.

If additional implants are needed and are going to be implanted in anoverlapping configuration, certain modifications to the technique aredesirable.

When implanting the first implant of an overlapping multiple implantconfiguration, make the initial defect 8.0-8.5 mm deep. This willprevent the implant from subsiding when the second implant slides downnext to it.

When implanting the first implant of an overlapping multiple implantconfiguration (a “snowman” configuration), ensure that the implant isoriented such that the seam or set of mating surfaces between the twoassembled demineralized cortical cap pieces (if the implant'sdemineralized cortical bone cap portion is assembled from two pieces ofcortical bone) is perpendicular to (or points to) the planned site ofthe second implant. About ⅓ of the first implant will be cored out, andcoring out evenly across the two assembled demineralized cortical bonecap pieces will minimize stress on the first implant during implantationof the second implant.

When coring the site for the second implant, core out no more than about⅓ of the first implant.

When implanting the second implant, the first implant will subside eventhough it is not being directly impacted. However, it may still beslightly proud when both implants are implanted. To complete theprocedure, tamp on both implants to ensure both implants are flush withthe native cartilage.

In the present specification, use of the singular includes the pluralexcept where specifically indicated. The use of the terms “a” and “an”and “the” and similar referents in the context of describing theinvention (especially in the context of the following claims) are to beconstrued to cover both the singular and the plural, unless otherwiseindicated herein or clearly contradicted by context. The terms“comprising,” “having,” “including,” and “containing” are to beconstrued as open-ended terms (meaning “including, but not limited to,”)unless otherwise noted. Whenever the term “about” appears before avalue, it should be understood that the specification is also providinga description of that value apart from the term “about”. Wherever anopen-ended term is used to describe a feature or element of theinvention, it is specifically contemplated that a closed-ended term canbe used in place of the open-ended term without departing from thespirit and scope of the invention. Recitation of ranges of values hereinare merely intended to serve as a shorthand method of referringindividually to each separate value falling within the range, unlessotherwise indicated herein, and each separate value is incorporated intothe specification as if it were individually recited herein. The use ofany and all examples, or exemplary language (e.g., “such as”) providedherein, is intended merely to better illuminate the invention and doesnot pose a limitation on the scope of the invention unless otherwiseclaimed. No language in the specification should be construed asindicating any non-claimed element as essential to the practice of theinvention.

In the present specification, any of the functions recited herein may beperformed by one or more means for performing such functions. Withrespect to the methods described in the specification, it is intendedthat the specification also provides a description of the products ofthose methods. With respect to the compositions and combinationsdescribed in the specification, it is intended that the specificationalso provides a description of the components, parts, portions, of suchcompositions and combinations.

All of the references cited herein, including patents, patentapplications, and publications, are hereby incorporated in theirentireties by reference.

While particular elements, embodiments and applications of the presentinvention have been shown and described, it will be understood, ofcourse, that the invention is not limited thereto since modificationscan be made by those skilled in the art without departing from the scopeof the present disclosure, particularly in light of the foregoingteachings.

Although the dependent claims have single dependencies in accordancewith U.S. patent practice, each of the features in any of the dependentclaims can be combined with each of the features of other dependentclaims or the main claim.

The invention claimed is:
 1. A bifunctional assembled implant adaptedfor implantation at a non-load bearing site of a bone cartilagejunction, comprising: an osteoconductive portion, comprising cancellousbone, adapted to fill a defect in a subchondral bone layer; and achondroinductive portion, comprising fully demineralized cortical bone,adapted to fill a cartilage layer adjacent to the subchondral bonelayer; wherein said osteoconductive portion and said chondroinductiveportion are assembled in a stacked relationship without separatefasteners or adhesives; wherein said osteoconductive portion and saidchondroinductive portion each defines a characteristic depth and acharacteristic width; and wherein said characteristic depth of saidosteoconductive portion is substantially equivalent to or greater thansaid characteristic depth of said chondroinductive portion; and whereinsaid osteoconductive portion and said chondroinductive portion areassembled to have an interference fit; and wherein said implant isadapted to backfill a secondary site created during an autograftcartilage repair procedure in a human patient.
 2. The implant of claim1, wherein said characteristic depth of said osteoconductive portion isat least about one and one half times greater than said characteristicdepth of said chondroinductive portion; and wherein said characteristicwidth of said osteoconductive portion is substantially the same as saidcharacteristic width of said chondroinductive portion.
 3. The implant ofclaim 1, wherein said interference fit is a hydration controlled shrinkfit.
 4. The implant of claim 1, wherein said interference fit furthercomprises a shaft and bore fit between said osteoconductive portion andsaid chondroinductive portion, and the shaft is straight or tapered. 5.The implant of claim 1, wherein said chondroinductive portion comprisesfrom two to eight pieces of cortical bone.
 6. The implant of claim 5,wherein said chondroinductive portion comprises two pieces of corticalbone.
 7. The implant of claim 6, wherein said two pieces of corticalbone each make up about one half of said chondroinductive portion. 8.The implant of claim 1, wherein said osteoconductive portionsubstantially surrounds at least one part of said chondroinductiveportion.
 9. The implant of claim 1, wherein said chondroinductiveportion comprises allograft bone, xenograft bone, or a combinationthereof.
 10. The implant of claim 1, wherein said cortical bone materialfurther includes one or more canals, said canals being oriented in adirection providing transport between said cancellous bone and saidcortical bone.
 11. A method of using an assembled osteochondral implant,comprising filling a defect site with said bifunctional assembledimplant of claim 1, such that a first region of said defect site isfilled by osteoconductive cancellous bone material and a second regionof said defect site is filled by chondroinductive cortical bonematerial.